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1

Features of formation of high-k dielectric layer in w/ultrathin HfO2/Si (100) structures under annealing  

NASA Astrophysics Data System (ADS)

The initial structures of two types - HfO2(50 nm)/Si (100) and W(150 nm)/HfO2(5 nm)/Si (100) - were prepared by radio frequency magnetron sputtering (RF-MS) in Ar+-plasma and further were subjected to the annealing at 500-950 °C followed by forming an ohmic contact to Si-substrate. Investigation of the first type structures show that differences in various crystalline modifications and kind of I-V curves strongly depend on conditions of growth of the HfO2 films during RF-MS process where RF bias Ubias, applying to the substrate, is an effective parameter for quality and growth process control of the HfO2 films. For the second type structures, the ultrathin HfO2 films were grown at Ubias= -7 V, then an effect of RTA at 950 °C in a neutral atmosphere on both electrical characteristics and chemical state at interfaces was studied. In comparison with as-deposited structures, RTA leads to decrease in the both the maximum specific capacitance in accumulation of C-V characteristics (by 30 %) and the dielectric constant (from 27 to 23). The thermally activated processes of formation of WOx phase at the W/HfO2 interface and Hf-silicate phase (HfSixOy) at the HfO2/Si (100) interface were observed. The total thickness of formed oxide layer exceeded the thickness of as-deposited HfO2 film by 30 %.

Rudakov, Valery I.; Bogoyavlenskaya, Elena A.; Denisenko, Yury I.; Naumov, V. V.

2013-01-01

2

HfO2 high-k dielectrics grown on (100)Ge with ultrathin passivation layers: Structure and interfacial stability  

NASA Astrophysics Data System (ADS)

We have investigated the growth of HfO2 thin films on (100)Ge by molecular beam epitaxy. By means of transmission electron microscopy, the structural characteristics of the films grown on clean Ge surfaces are compared with those grown on passivation layers of GeOx and GeOxNy. The interface was found to be very flat and thin, with an interfacial layer one or two monolayer thick. However, traces of Ge in the oxide have been detected when deposited on either one of the interfacial layers, which can be explained by the instability of the interfacial layers grown with an atomic oxygen/nitrogen beam, prior to the HfO2 deposition.

Seo, J. W.; Dieker, Ch.; Locquet, J.-P.; Mavrou, G.; Dimoulas, A.

2005-11-01

3

Characteristics of sandwich-structured Al 2O 3/HfO 2/Al 2O 3 gate dielectric films on ultra-thin silicon-on-insulator substrates  

NASA Astrophysics Data System (ADS)

Sandwich-structure Al 2O 3/HfO 2/Al 2O 3 gate dielectric films were grown on ultra-thin silicon-on-insulator (SOI) substrates by vacuum electron beam evaporation (EB-PVD) method. AFM and TEM observations showed that the films remained amorphous even after post-annealing treatment at 950 °C with smooth surface and clean silicon interface. EDX- and XPS-analysis results revealed no silicate or silicide at the silicon interface. The equivalent oxide thickness was 3 nm and the dielectric constant was around 7.2, as determined by electrical measurements. A fixed charge density of 3 × 10 10 cm -2 and a leakage current of 5 × 10 -7A/cm 2 at 2 V gate bias were achieved for Au/gate stack /Si/SiO 2/Si/Au MIS capacitors. Post-annealing treatment was found to effectively reduce trap density, but increase in annealing temperature did not made any significant difference in the electrical performance.

Cheng, Xinhong; Song, Zhaorui; Jiang, Jun; Yu, Yuehui

2005-12-01

4

Atomic layer etching of ultra-thin HfO2 film for gate oxide in MOSFET devices  

Microsoft Academic Search

Precise etch depth control of ultra-thin HfO2 (3.5 nm) films applied as a gate oxide material was investigated by using atomic layer etching (ALET) with an energetic Ar beam and BCl3 gas. A monolayer etching condition of 1.2 Å\\/cycle with a low surface roughness and an unchanged surface composition was observed for ultra-thin, ALET-etched HfO2 by supplying BCl3 gas and

Jae Beom Park; Woong Sun Lim; Byoung Jae Park; Ih Ho Park; Young Woon Kim; Geun Young Yeom

2009-01-01

5

Atomic layer etching of ultra-thin HfO 2 film for gate oxide in MOSFET devices  

Microsoft Academic Search

Precise etch depth control of ultra-thin HfO2 (3.5nm) films applied as a gate oxide material was investigated by using atomic layer etching (ALET) with an energetic Ar beam and BCl3 gas. A monolayer etching condition of 1.2Å\\/cycle with a low surface roughness and an unchanged surface composition was observed for ultra-thin, ALET-etched HfO2 by supplying BCl3 gas and an Ar

Jae Beom Park; Woong Sun Lim; Byoung Jae Park; Young Woon Kim; Geun Young Yeom

2009-01-01

6

Compatibility of polycrystalline silicon gate deposition with HfO2 and Al2O3/HfO2 gate dielectrics  

NASA Astrophysics Data System (ADS)

Polycrystalline-silicon (poly-Si) gate compatibility issues with HfO2 and Al2O3 capped HfO2 gate dielectrics are reported. It can be generally stated that chemical vapor deposition (CVD) silicon gates using silane deposited directly onto HfO2 results in electrical properties much worse compared to similar HfO2 films using platinum metal gates. However, depositing CVD silicon gates directly onto Al2O3 capped HfO2 showed greater than a 104 times reduction in gate leakage compared to the poly-Si/HfO2 and poly-Si/SiO2 controls of similar electrical thickness.

Gilmer, D. C.; Hegde, R.; Cotton, R.; Garcia, R.; Dhandapani, V.; Triyoso, D.; Roan, D.; Franke, A.; Rai, R.; Prabhu, L.

2002-08-01

7

Characterization and comparison of the charge trapping in HfSiON and HfO2 gate dielectrics  

Microsoft Academic Search

Charge trapping in HfSiON and HfO2 gate dielectrics was studied using both DC and pulsed ID-VG characterization techniques. The data shows a significant amount of hysteresis in HfO2 but negligible instability in HfSiON. Constant voltage stress measurements of HfO2 and HfSiON films show that the threshold voltage shift in HfO2 films is as much as 10 times higher than that

A. Shanware; M. R. Visokay; J. J. Chambers; A. L. P. Rotondaro; J. McPherson; L. Colombo

2003-01-01

8

Cubic HfO2 Doped with Y2O3 for Advanced Gate Dielectrics by MBE  

Microsoft Academic Search

High kappa HfO2 (kappa =20) is currently employed as an alternative gate dielectric replacing SiO2 in CMOS scaling. There are three known crystal structures of HfO2, monoclinic, cubic, and tetragonal with varying dielectric constants [1]. Recently we showed HfO2 films epitaxially grown on GaAs(100) formed the stable monoclinic phase (alpha=gamma = 90° and beta ˜ 99°) with the a and

Zhikai Yang; W. C. Lee; Pen Chang; Molin Huang; Yi Lin Huang; Minghwei Hong; C. M. Huang; C. H. Hsu; Raynien Kwo

2006-01-01

9

Resistive switching effects of HfO 2 high- k dielectric  

Microsoft Academic Search

Resistive switching behavior of HfO2 high-k dielectric has been studied as a promising candidate for emerging non-volatile memory technology. The low resistance ON state and high resistance OFF state can be reversibly altered under a low SET\\/RESET voltage of ±3V. The memory device shows stable retention behavior with the resistance ratio between both states maintained greater than 103. The bipolar

M. Y. Chan; T. Zhang; V. Ho; P. S. Lee

2008-01-01

10

Breakdown mechanism for the thin EOT Dy2O3\\/HfO2 dielectric  

Microsoft Academic Search

The intrinsic time dependent dielectric breakdown (TDDB) of the thin bilayered Dy2O3\\/HfO2 gate oxide has been studied. A physical based breakdown model has been developed and can be used to predict the lifetime for the lower stress voltage and extract the defect density by introducing the effective oxide thinning model. This model has also been extended to include temperature dependency

Tackhwi Lee; Sung Il Park; J. C. Lee; S. K. Banerjee

2008-01-01

11

Cubic HfO2 Doped with Y2O3 for Advanced Gate Dielectrics by MBE.  

NASA Astrophysics Data System (ADS)

High ? HfO2 (? =20) is currently employed as an alternative gate dielectric replacing SiO2 in CMOS scaling. There are three known crystal structures of HfO2, monoclinic, cubic, and tetragonal with varying dielectric constants [1]. Recently we showed HfO2 films epitaxially grown on GaAs(100) formed the stable monoclinic phase (?=? = 90° and ? ˜ 99°) with the a and b axes aligned with the in-plane GaAs100axes resulting in four equivalent domains. This work demonstrates the successful alteration of the crystal structure of HfO2 from the lower ? monoclinic phase to the higher ? (? =30) cubic phase stabilized through epitaxy on GaAs(100) and Si(100) with the aid of Y2O3 doping (˜ 20% based on XPS). X-ray diffraction scans on these films clearly indicated the cubic symmetry. Doping Y2O3 is also to enhance the thermal stability of amorphous HfO2. Y2O3 doping was shown to help raise the re-crystallization temperature of HfO2 to becompatible with high temperature processing. [1] X. Zhao et al, PRB 65, 233106, (2002).

Yang, Zhikai; Lee, W. C.; Chang, Pen; Huang, Molin; Huang, Yi Lin; Hong, Minghwei; Huang, C. M.; Hsu, C. H.; Kwo, Raynien

2006-03-01

12

Internal dielectric interface: SiO2- HfO2  

NASA Astrophysics Data System (ADS)

Hafnia is the leading candidate to replace silica as the gate dielectric in CMOS technology. Typically, hafnia films are deposited by atomic layer deposition (ALD) on the oxidized surface of a silicon wafer. The oxide could be native or thermally grown. Therefore, the high-k dielectric film is not in direct contact with Si, but rather with silicon dioxide. We investigate theoretically the atomic structure of the SiO2-HfO2 interface, its energretics, and thermodynamic stability with respect to oxygen exchange across the interface. We have examined the electronic properties of the interface including the band discontinuity using density functional theory. To model the interface we build a supercell structure by connecting ?-crystobalite (crystalline silica polymorph) and cubic hafnia. This model, while being obviously rather simplistic allows for systematic study of the dielectric thickness effects, and consistent placement of defects with respect to the interface. The striking atomic feature of the calculated interface structure is three-fold coordinated interfacial oxygen atoms connected to one Si and two Hf neighbors. The Si-O and Hf-O bond lengths are 1.62 and 2.1 å, respectively. The energy of the interface is estimated to be in the range of 900-4000 erg/cm^2 depending on the oxygen chemical potential. The structure has no states in the gap, and the estimated valence band offset agrees well with the MIGS theory. We discuss the effect of vacancies on the band alignment, and possible implications of our results to Si-SiO2-HfO2-Metal stacks.

Sharia, Onise; Demkov, Alex; Bersuker, Genadi; Lee, Byoung Hun

2006-03-01

13

Photo-induced tunneling currents in MOS structures with various HfO2/SiO2 stacking dielectrics  

NASA Astrophysics Data System (ADS)

In this study, the current conduction mechanisms of structures with tandem high-k dielectric in illumination are discussed. Samples of Al/SiO2/Si (S), Al/HfO2/SiO2/Si (H), and Al/3HfO2/SiO2/Si (3H) were examined. The significant observation of electron traps of sample H compares to sample S is found under the double bias capacitance-voltage (C-V) measurements in illumination. Moreover, the photo absorption sensitivity of sample H is higher than S due to the formation of HfO2 dielectric layer, which leads to larger numbers of carriers crowded through the sweep of VG before the domination of tunneling current. Additionally, the HfO2 dielectric layer would block the electrons passing through oxide from valance band, which would result in less electron-hole (e--h+) pairs recombination effect. Also, it was found that both of the samples S and H show perimeter dependency of positive bias currents due to strong fringing field effect in dark and illumination; while sample 3H shows area dependency of positive bias currents in strong illumination. The non-uniform tunneling current through thin dielectric and through HfO2 stacking layers are importance to MOS(p) tunneling photo diodes.

Pang, Chin-Sheng; Hwu, Jenn-Gwo

2014-04-01

14

Properties of HfO2/ultrathin SiO2/Si structures and their comparison with Si MOS structures passivated in KCN solution  

NASA Astrophysics Data System (ADS)

Electrical, optical and partly structural properties are investigated on very thin ALD HfO2/ultrathin NAOS SiO2/n-type Si structures. An ALD layer was deposited at 250 °C and it contains amorphous and crystalline–probably monoclinic HfO2 phases. HfO2 films with both types of structural phases were not stable if thermal treatment above 200 °C was applied. On as- prepared samples, deep interface traps with activation energy of ?W = 0.23 eV have been determined. After annealing of the structure at 200 °C, the traps were partly transformed and a mid-gap level ?W = 0.49 eV was detected. FTIR and AFM measurements confirmed presence of HfO2 monoclinic phase in the HfO2 films. On the other side, the density of interface defect states of the structure decreased from approx. 1012 eV?1 cm?2 to 1011 eV?1 cm?2 after low temperature annealing of the reference structure. The results are compared with very similar (almost identical) development of interface defect states on the very thin thermal SiO2/Si structure before and after passivation in a 0.1 M KCN methanol solution.PACS: 78.55.Qr; 78.66.Jg; 81.16.Pr; 85.40Ls

Pin?ík, Emil; Kobayashi, Hikaru; Matsumoto, Taketoshi; Takahashi, Masao; Mikula, Milan; Brunner, Róbert

2014-05-01

15

Photoreflectance Spectroscopic Characterization of Si with SiO2 and HfO2 Dielectric Layers  

NASA Astrophysics Data System (ADS)

Photoreflectance (PR) spectroscopy is employed as a non-destructive and contactless technique for the characterization of silicon with SiO2 and HfO2 dielectric layers. The position of PR spectra reveals the critical point energy and the magnitude indicates the surface potential in silicon. By fitting PR spectra to a third-derivative functional form, we find the critical point of silicon with a 1.0 nm SiO2 layer is 3.42 eV. The PR magnitude of samples with HfO2 dielectric layer decreases with layer thickness. This indicates the decreasing of surface potential with high-? layer thickness, possibly due to increased charge defects in the layer.

Zhang, Tianhao; di, Ming; Bersch, Eric J.; Chouaib, Houssam; Salnik, Alex; Nicolaides, Lena; Bevis, Chris; Consiglio, Steven; Clark, Robert D.; Diebold, Alain C.

2009-09-01

16

Improvement of write\\/erase cycling of memory cells with SiO2\\/HfO2 tunnel dielectric  

Microsoft Academic Search

The write\\/erase endurance of low voltage floating gate memory cells programmed and eased by tunneling through a SiO2\\/HfO2 dual layer tunnel dielectric stack is investigated. The used of fixed single pulse program and erase conditions lead to fast shifting (after ?1000 cycles) of the threshold voltage window, so that only a limited number of write\\/erase cycles can be achieved. Increasing

P. Blomme; B. Govoreanu; J. Van Houdt; K. De Meyer

2003-01-01

17

Effective control of flat-band voltage in HfO2 gate dielectric with La2O3 incorporation  

Microsoft Academic Search

The origin of negative flat-band shift using La2O3 incorporation in HfO2 dielectrics has been extensively examined. From careful extraction of effective work function of gate electrode and fixed charges at each interface, it has been revealed that La2O3 at high-k\\/Si substrate or high-k\\/SiO2 interface has either large amount of positive fixed charges or an additional dipole of 0.36 V compared

K. Okamoto; M. Adachi; K. Kakushima; P. Ahmet; N. Sugii; K. Tsutsui; T. Hattori; H. Iwai

2007-01-01

18

Ge MOS characteristics with CVD HfO2 gate dielectrics and TaN gate electrode  

Microsoft Academic Search

In this paper, we report for the first time Ge MOS characteristics with ultra thin rapid thermal CVD HfO2 gate dielectrics and TaN gate electrode. Using the newly developed pre-gate cleaning and NH3-based Ge surface passivation, the TaN\\/HfO2\\/Ge gate stack with EOT of 12.9 Å exhibits excellent leakage current density of 6 mA\\/cm2 @Vg=1V and interface state density (Dit) of

W. P. Bai; N. Lu; J. Liu; A. Ramirez; D. L. Kwong; D. Wristers; A. Ritenour; L. Lee; D. Antoniadis

2003-01-01

19

Dependence of the band gap in the high-k dielectric HfO2 on crystalline phase  

NASA Astrophysics Data System (ADS)

Recently HfO2 has attracted considerable attention as a gate dielectric for (CMOS) CMOS technology, because it combines a wide band gap and good thermal stability with a low-frequency dielectric constant much higher than that of SiO2. While the exact values of the band gap and band alignment with Si(001) are important for the application as gate dielectric, experimental data show some scatter possibly due to ill-defined crystallinity of the samples. We analyze the structural and electronic properties of both cubic and tetragonal HfO2 employing density-functional theory within the local-density approximation (LDA) in a pseudopotentials, plane-wave approach. We find that cubic HfO2 has a direct band gap, while the tetragonal phase exhibits a slightly larger indirect gap. Applying many-body perturbation theory in the GW approximation corrects the underestimation of the LDA band gap and gives band gaps within the experimentally reported range. We find that the energy shifts introduced by the GW self-energy are largely independent of the structure and show that the differences in band structure between the two phases arise mainly from internal relaxations of the oxygen atoms in the tetragonal phase, while the c/a value has little effect on the character of the band gap.

Nishitani, K.

2005-03-01

20

Breakdown mechanism for the thin EOT Dy2O3\\/HfO2 dielectrics  

Microsoft Academic Search

Intrinsic TDDB of the thin bilayered Dy2O3\\/HfO2 gate oxide has been discussed Physical based breakdown model suggested Defect density extracted by introducing the oxide thinning model The effective activation energy is calculated

Tackhwi Lee; Jack Lee; Sanjay K. Banerjee

2008-01-01

21

Amorphous stability of HfO 2 based ternary and binary composition spread oxide films as alternative gate dielectrics  

NASA Astrophysics Data System (ADS)

A ternary alloyed thin film library of HfO 2-Y 2O 3-Al 2O 3 was grown on a Si(1 0 0) substrate in a few hours by a new pulsed laser deposition (PLD) system installed with a masking and substrate rotating scheme. This specially designed combinatorial ternary composition spread method enabled us to fabricate continuous ternary and binary composition spread film libraries. It is noteworthy that the library made by this system is addressable; each film composition covers the full range (from 0 to 100%) and can be directly correlated with the film location in the ternary and binary phase diagram. Rapid permittivity measurement on the film libraries was carried out by a scanning microwave microscope, while the crystal structure was by a combinatorial X-ray diffractometer (XRD). The (HfO 2) 6(Y 2O 3) 1(Al 2O 3) 3 ternary composition area in an amorphous phase was found to have a dielectric constant higher than HfO 2-Y 2O 3 binary area. This ternary oxide is promising as amorphous gate dielectric material.

Hasegawa, K.; Ahmet, P.; Okazaki, N.; Hasegawa, T.; Fujimoto, K.; Watanabe, M.; Chikyow, T.; Koinuma, H.

2004-02-01

22

Comparison of interfacial and electrical characteristics of HfO2 and HfAlO high-k dielectrics on compressively strained Si1-xGex  

NASA Astrophysics Data System (ADS)

Interfacial reactions and electrical properties of HfO2 and HfAlO high-k gate dielectric films on strained Si1-xGex (x=17%) fabricated by pulsed-laser deposition were investigated. The dielectric films were characterized by x-ray photoelectron spectroscopy, transmission electron microscopy, and electrical measurements. We found that alloying of HfO2 with alumina can reduce the GeOx formation at the interfacial layer and thus reduce the Ge diffusion during the film post-thermal annealing process. Such suppression effect significantly improved the electrical properties of the dielectric films.

Curreem, K. K. S.; Lee, P. F.; Wong, K. S.; Dai, J. Y.; Zhou, M. J.; Wang, J.; Li, Quan

2006-05-01

23

Interface effect on dielectric constant of HfO2/Al2O3 nanolaminate films deposited by plasma-enhanced atomic layer deposition  

NASA Astrophysics Data System (ADS)

The effect of the interface between Al2O3 and HfO2 sublayers on the dielectric constant was investigated in HfO2/Al2O3 nanolaminate films deposited using plasma-enhanced atomic layer deposition. After annealing at 700 °C, the dielectric constants of the nanolaminate films with a sublayer thickness of 40 A? or greater were the same as the calculated values for a series of capacitors consisting of amorphous Al2O3 and monoclinic or tetragonal HfO2. As the sublayer thickness was reduced to 10 A?, the dielectric constant increased up to 17.7 because a thin Hf-O-Al mixture layer, of which the number increases drastically in the nanolaminate films with thin sublayers, is formed at the interface.

Park, Pan Kwi; Cha, Eun-Soo; Kang, Sang-Won

2007-06-01

24

A Dy2O3-capped HfO2 Dielectric and TaCx-based Metals Enabling Low-Vt Single-Metal-Single-Dielectric Gate Stack  

Microsoft Academic Search

We show for the first time that conduction and valence band-edge effective work functions (WF) are achieved simultaneously by one single Dy2O3 capping layer on HfO2 for both nMOS and pMOS with TaCx-based metals. Low Vt's (0.23 and -0.36 V) are obtained without degrading the EOT-JG scalability and hole mobility. A model based on competing intermixes of cap\\/host dielectric and

V. S. Chang; L.-A. Ragnarsson; G. Pourtois; R. O'Connor; C. Adelmann; S. Van Elshocht; A. Delabie; J. Swerts; N. Van der Heyden; T. Conard; H.-J. Cho; A. Akheyar; R. Mitsuhashi; T. Witters; B. J. O'Sullivan; L. Pantisano; E. Rohr; P. Lehnen; S. Kubicek; T. Schram; S. De Gendt; P. P. Absil; S. Biesemans

2007-01-01

25

Surface passivation using ultrathin AlNx film for Ge-metal-oxide-semiconductor devices with hafnium oxide gate dielectric  

NASA Astrophysics Data System (ADS)

A surface passivation method to improve the film quality of HfO2 gate dielectric on Ge substrate by using ultrathin AlNx layer is reported. Results show that the AlNx passivation layer is more effective in suppressing the GeOx formation at the HfO2/Ge interface, resulting in improved C-V characteristics, than surface nitridation-passivated Ge devices. In addition, a thermal stability study shows AlNx passivation is promising for future Ge metal-oxide-semiconductor devices.

Gao, Fei; Lee, S. J.; Pan, J. S.; Tang, L. J.; Kwong, Dim-Lee

2005-03-01

26

Improved MOSFET characteristics by Incorporating Laminated Dysprosium (Dy2O3) Dielectric into HfO2 Gate Stack  

Microsoft Academic Search

New structural approach of Dy2O3 incorporated HfO2 multi-metal oxide n-MOSFETs and their electrical characterization are investigated for the first time. Top Dy2O3 laminated HfO2 bi-layer structure shows the thinnest EOT with reduced leakage current compared to control HfO2. Improved electrical characteristics such as lower VT, higher drive current and channel electron mobility are demonstrated. In addition, better VT instabilities, reduced

Tackhwi Lee; Se Jong Rhee; Chang Yong Kang; Feng Zhu; Manhong Zhang; Hyoung-sub Kim; Changhwan Choi; Sergei Koveshnikov; J. C. Lee

2006-01-01

27

Low-voltage pentacene organic field-effect transistors with high-kappa HfO2 gate dielectrics and high stability under bias stress  

Microsoft Academic Search

Low-voltage pentacene organic field-effect transistors are demonstrated (operating voltage of -3 V) with high-kappa hafnium dioxide gate dielectrics grown by atomic layer deposition at 200 °C. A high hole mobility of 0.39 cm2\\/V s with low threshold voltage (<-0.5 V) and low subthreshold slope of 120 mV\\/dec is achieved with a HfO2 dielectric layer modified with a phosphonic acid based

Xiao-Hong Zhang; Shree Prakash Tiwari; Sung-Jin Kim; Bernard Kippelen

2009-01-01

28

HfO2 dielectrics engineering using low power SF6 plasma on InP and In0.53Ga0.47As metal-oxide-semiconductor field-effect-transistors  

NASA Astrophysics Data System (ADS)

In this work, we demonstrate that device characteristics could be significantly improved by incorporating more fluorine (F) into HfO2 dielectrics layer using low power SF6 plasma treatment at different positions of gate oxide. Fluorine was incorporated in three ways: 4 min treatment from the top of 6 nm HfO2, 4 min treatment in the middle of 6 nm HfO2, or 2 min treatment each in the middle and from the top of HfO2 layer. Drive current (Id) and effective channel mobility could be improved by 70% and 51%, respectively, for devices with treatment both in the middle and from the top of HfO2 high ? layer compared to those of devices without SF6 treatment. The impact of SF6 plasma treatment on devices with HfO2/In0.53Ga0.47As stack is also presented.

Wang, Yanzhen; Chen, Yen-Ting; Xue, Fei; Zhou, Fei; Lee, Jack C.

2012-06-01

29

Comparative study of pulsed laser deposited HfO2 and Hf-aluminate films for high-k gate dielectric applications  

NASA Astrophysics Data System (ADS)

The thermal stability and the electrical properties of HfO2 and Hf-aluminate films prepared by the pulsed laser deposition technique have been investigated by X-ray diffraction, differential thermal analysis, capacitance-voltage correlation, leakage-current measurements and high-resolution transmission electron microscopy observation, respectively. A crystallization transformation from HfO2 amorphous phase to polycrystalline monoclinic structure occurs at about 500 °C. In contrast, the amorphous structure of Hf-aluminate films remains stable at higher temperatures up to 900 °C. Rapid thermal annealing at 1000 °C for 3 min leads to a phase separation in Hf-aluminate films. Tetragonal HfO2(111) is predominant, and Al2O3 separates from Hf-aluminate and is still in the amorphous state. The dielectric constant of amorphous HfO2 and Hf-aluminate films was determined to be about 26 and 16.6, respectively, by measuring a Pt/dielectric film/Pt capacitor structure. A very small equivalent oxide thickness (EOT) value of 0.74 nm for a 3-nm physical thickness Hf-aluminate film on a n-Si substrate with a leakage current of 0.17 A/cm2 at 1-V gate voltage was obtained. The interface at Hf-aluminate/Si is atomically sharp, while a thick interface layer exists between the HfO2 film and the Si substrate, which makes it difficult to obtain an EOT of less than 1 nm.

Zhu, J.; Liu, Z. G.

2005-05-01

30

Dielectric relaxation and Charge trapping characteristics study in Germanium based MOS devices with HfO2 \\/Dy2O3 gate stacks  

Microsoft Academic Search

In the present work we investigate the dielectric relaxation effects and charge trapping characteristics of HfO2 \\/Dy2O3 gate stacks grown on Ge substrates. The MOS devices have been subjected to constant voltage stress (CVS) conditions at accumulation and show relaxation effects in the whole range of applied stress voltages. Applied voltage polarities as well as thickness dependence of the relaxation

M. Shahinur Rahman; E. K. Evangelou

2011-01-01

31

Performance and reliability of ultra thin CVD HfO2 gate dielectrics with dual poly-Si gate electrodes  

Microsoft Academic Search

MOSFETs with high quality ultra thin (EOT~10.3 Å) HfO2 gate stacks and self-aligned dual poly-Si gate are fabricated and characterized. Both n- and p-MOSFETs show good electron and hole mobility, respectively, and excellent sub-threshold swings. In addition, the HfO2 gate stack exhibits excellent thermal stability with poly-Si gates up to 1050°C\\/30 s gate activation annealing and shows excellent TDDB reliability

S. J. Lee; H. F. Luan; C. H. Lee; T. S. Jeon; W. P. Bai; Y. Senzaki; D. Roberts; D. L. Kwong

2001-01-01

32

Electrical characteristics of postdeposition annealed HfO2 on silicon  

Microsoft Academic Search

Electrical characteristics of ultrathin HfO2 films on p-type silicon (100) substrates were determined by capacitance-voltage and current density-voltage measurements. The as-deposited HfO2 films showed a dielectric constant of ~22, a leakage current density of 5 A\\/cm2 and an interface state density of 6.5×1012 cm2 eV-1 at an equivalent oxide thickness (EOT) of 7.6 A˚ due to the poor quality of

Ragesh Puthenkovilakam; Monica Sawkar; Jane P. Chang

2005-01-01

33

Effects of charge and dipole on flatband voltage in an MOS device with a Gd-doped HfO2 dielectric  

NASA Astrophysics Data System (ADS)

Gd-doped HfO2 has drawn worldwide interest for its interesting features. It is considered to be a suitable material for N-type metal-oxide-semiconductor (MOS) devices due to a negative flatband voltage (Vfb) shift caused by the Gd doping. In this work, an anomalous positive shift was observed when Gd was doped into HfO2. The cause for such a phenomenon was systematically investigated by distinguishing the effects of different factors, such as Fermi level pinning (FLP), a dipole at the dielectric/SiO2 interface, fixed interfacial charge, and bulk charge, on Vfb. It was found that the FLP and interfacial dipole could make Vfb negatively shifted, which is in agreement with the conventional dipole theory. The increase in interfacial fixed charge resulting from Gd doping plays a major role in positive Vfb shift.

Han, Kai; Wang, Xiao-Lei; Yang, Hong; Wang, Wen-Wu

2013-11-01

34

Memory Effect of Metal-Oxide-Silicon Capacitors with Self-Assembly Double-Layer Au Nanocrystals Embedded in Atomic-Layer-Deposited HfO2 Dielectric  

NASA Astrophysics Data System (ADS)

We report the chemical self-assembly growth of Au nanocrystals on atomic-layer-deposited HfO2 films aminosilanized by (3-Aminopropyl)-trimethoxysilane aforehand for memory applications. The resulting Au nanocrystals show a density of about 4 × 1011 cm-2 and a diameter range of 5-8nm. The metal-oxide-silicon capacitor with double-layer Au nanocrystals embedded in HfO2 dielectric exhibits a large C - V hysteresis window of 11.9V for ±11 V gate voltage sweeps at 1 MHz, a flat-band voltage shift of 1.5 V after the electrical stress under 7 V for 1 ms, a leakage current density of 2.9 × 10-8 A/cm-2 at 9 V and room temperature. Compared to single-layer Au nanocrystals, the double-layer Au nanocrystals increase the hysteresis window significantly, and the underlying mechanism is thus discussed.

Huang, Yue; Gou, Hong-Yan; Sun, Qing-Qing; Ding, Shi-Jin; Zhang, Wei; Zhang, Shi-Li

2009-10-01

35

Effect of low temperature annealing on the electrical properties of an MOS capacitor with a HfO2 dielectric and a TiN metal gate  

NASA Astrophysics Data System (ADS)

The effects of low temperature annealing, such as post high-k dielectric deposition annealing (PDA), post metal annealing (PMA) and forming gas annealing (FGA) on the electrical characteristics of a metal—oxide—semiconductor (MOS) capacitor with a TiN metal gate and a HfO2 dielectric are systematically investigated. It can be found that the low temperature annealing can improve the capacitance—voltage hysteresis performance significantly at the cost of increasing gate leakage current. Moreover, FGA could effectively decrease the interfacial state density and oxygen vacancy density, and PDA could make the flat band positively shift which is suitable for P-type MOSs.

Kai, Han; Xueli, Ma; Jinjuan, Xiang; Hong, Yang; Wenwu, Wang

2013-11-01

36

Ultra-thin (Teff inv = 1.7 nm) poly-Si-gated SiN\\/HfO2\\/SiON high-k stack dielectrics with high thermal stability (1050°C)  

Microsoft Academic Search

Demonstrated the high-performance and high-reliability of ultra-thin poly-Si-gated SiN\\/HfO2\\/SiON high-k stack dielectrics. A SiN layer deposited on HfO2 is shown to be indispensable to the suppression of the reaction of poly-Si and HfO2, resulting in high thermal stability (1050°C). This thermally stable SiN\\/HfO2\\/SiON structure can achieve an ultrathin oxide thickness of Teffinv (effective oxide thickness measured in strong inversion region)

Y. Morisaki; T. Aoyama; Y. Sugita; K. Irino; T. Sugii; T. Nakamura

2002-01-01

37

A Comparison of Al2O3\\/HfO2 and Al2O3\\/ZrO2 Bilayers Deposited by the Atomic Layer Deposition Method for Potential Gate Dielectric Applications  

Microsoft Academic Search

Thin films of Al2O3\\/HfO2 and Al2O3\\/ZrO2 bilayers were investigated as potential replacements for traditional SiO2 gate dielectrics. The Al2O3 film exhibited an amorphous structure without an interfacial layer, while the HfO2 and ZrO2 films had randomly oriented polycrystalline structures with a silicate interlayer. The two gate oxides, Al2O3 and HfO2, have characteristics that are complementary to each other, and it

Inhoe Kim; Jaehyoung Koo; Janghee Lee; Hyeongtag Jeon

2006-01-01

38

Surface NH3 anneal on strained Si0.5Ge0.5 for metal-oxide-semiconductor applications with HfO2 as gate dielectric  

NASA Astrophysics Data System (ADS)

In this Letter, metal-oxide-semiconductor capacitors were fabricated and characterized on compressively strained Si50Ge50 on Si0.8Ge0.2 virtual substrates by using metal-organic chemical vapor deposition HfO2 as gate dielectric and TaN as metal gate electrode. It is demonstrated that surface nitridation treatment using NH3 annealing prior to HfO2 deposition effectively prevents the growth of GeOx at the interfacial layer which exists on SiGe surface with direct deposition of HfO2. X-ray photoelectron spectroscopic analysis suggests that the nitridation process tends to occur to Si atoms rather than to Ge atoms and results in the formation of an interfacial layer of SiNxOy on the SiGe surface. Capacitors with the surface nitridation treatment show good capacitance-voltage characteristics with negligible hysteresis, much smaller interface trap charge density, and significantly improved gate leakage current in comparison with those of capacitors made without nitridation treatment. The surface nitridation seems to be a promising method for the formation of high quality high-? gate stack on strained SiGe substrate.

Huang, Jidong; Wu, Nan; Zhang, Qingchun; Zhu, Chunxiang; Li, M. F.; Tay, Andrew A. O.; Cheng, Zhi-Yuan; Leitz, Chris W.; Lochtefeld, Anthony

2006-04-01

39

Influence of radial stress on the performance of gate-all-around Ge(110) NW FETs with HfO2 dielectric.  

PubMed

In this work, a simulation method from strained valence band structures to strained mobility calculation to consider a radial stress at the boundary of HfO2 gate dielectric surrounding Ge(110) nanowire is developed. The simulation implements the radial stress to strain distribution calculation via finite element method and then to valence band calculation. The radial stress at the boundary of gate dielectric pushes the valence subbands downwards in contrast with lattice mismatch strain effects between Ge NW and gate dielectric. The impact of the radial stress on the hole effective masses and density of states of HfO2 gate dielectric surrounding Ge(110) nanowire are also investigated. The potential distribution and holes density distribution are calculated by solving the 2D Poisson equation and Schrödinger equation self-consistently in NW cross section. Hole mobility is obtained by modified Kubo-Greenwood formula. Based on strained valence band structures, the hole density distribution in cross-sectional Ge(110) NW reduces with larger radial stress value. The phonon scattering-limited hole mobility in NW significantly increases as the radial stress increases. PMID:22408941

Xu, Honghua; Liu, Xiaoyan; Du, Gang; He, Yuhui; Fan, Chun; Han, Ruqi; Kang, Jinfeng

2011-12-01

40

Influence of O2 flow rate on HfO2 gate dielectrics for back-gated graphene transistors  

NASA Astrophysics Data System (ADS)

HfO2 thin films deposited on Si substrate using electron beam evaporation, are evaluated for back-gated graphene transistors. The amount of O2 flow rate, during evaporation is optimized for 35 nm thick HfO2 films, to achieve the best optical, chemical and electrical properties. It has been observed that with increasing oxygen flow rate, thickness of the films increased and refractive index decreased due to increase in porosity resulting from the scattering of the evaporant. The films deposited at low O2 flow rates (1 and 3 SCCM) show better optical and compositional properties. The effects of post-deposition annealing and post-metallization annealing in forming gas ambience (FGA) on the optical and electrical properties of the films have been analyzed. The film deposited at 3 SCCM O2 flow rate shows the best properties as measured on MOS capacitors. To evaluate the performance of device properties, back-gated bilayer graphene transistors on HfO2 films deposited at two O2 flow rates of 3 and 20 SCCM have been fabricated and characterized. The transistor with HfO2 film deposited at 3 SCCM O2 flow rate shows better electrical properties consistent with the observations on MOS capacitor structures. This suggests that an optimum oxygen pressure is necessary to get good quality films for high performance devices.

Lakshmi Ganapathi, Kolla; Bhat, Navakanta; Mohan, Sangeneni

2014-05-01

41

Physical model of BTI, TDDB and SILC in HfO2-based high-k gate dielectrics  

Microsoft Academic Search

The microscopic mechanism of the degradation occurring in HfO2-based high-k\\/IL dual layer gate insulator has been investigated. The hole-injection-induced release of hydrogen from Si-H terminations causes IL-breakdown. This mechanism accelerates NBTI. Defects due to electron-trapped oxygen vacancies are the origin of trap-assisted tunneling, causing SILC in the electron current and PBTI.

K. Torii; H. Kitajima; T. Arikado; K. Shiraishi; S. Miyazaki; K. Yamabe; M. Boero; T. Chikyow; K. Yamada

2004-01-01

42

Top-Gated Graphene Nanoribbon Transistors with Ultra-Thin High-k Dielectrics  

PubMed Central

The integration ultra-thin high dielectric constant (high-k) materials with graphene nanoribbons (GNRs) for top-gated transistors can push their performance limit for nanoscale electronics. Here we report the assembly of Si/HfO2 core/shell nanowires on top of individual GNRs as the top-gates for GNR field-effect transistors with ultra-thin high-k dielectrics. The Si/HfO2 core/shell nanowires are synthesized by atomic layer deposition of HfO2 shell on highly-doped silicon nanowires with a precise control of the dielectric thickness down to 1–2 nm. Using the core/shell nanowires as the top-gates, high performance GNR transistors have been achieved with transconductance reaching 3.2 mS ?m?1, the highest value for GNR transistors reported to date. This method, for the first time, demonstrates the effective integration of ultra-thin high-k dielectrics with graphene with precisely controlled thickness and quality, representing an important step towards high performance graphene electronics.

Liao, Lei; Bai, Jingwei; Cheng, Rui; Lin, Yungchen; Jiang, Shan; Huang, Yu; Duan, Xiangfeng

2010-01-01

43

Thermodynamic Stability of High-K Dielectric Metal Oxides ZrO2 and HfO2 in Contact with Si and SiO_2  

NASA Astrophysics Data System (ADS)

It is known that the chemistries of hafnium and zirconium are more nearly identical than for any other two congeneric elements. Thus, both zirconia, with the dielectric constant K of 22, and hafnia (K = 21) have emerged as potential replacements for silica (K = 3.9) as a gate dielectric. Our theoretical and experimental results indicate that there is an important difference between the zirconia/Si and hafnia/Si interfaces. The former was found to be unstable with respect to formation of silicides whereas the latter is stable. The MO_2/SiO2 interface is marginally unstable with respect to formation of silicates (M=Zr and Hf). Cross-sectional transmission electron micrographs expose formation of nodules, identified as silicides, across the polysilicon/ZrO_2/Si interfaces but not for the interfaces with HfO_2. For both ZrO2 and HfO_2, the X-ray photoemission spectra illustrate formation of silicate-like compounds in the MO_2/SiO2 interface. The calculations were performed in the framework of density functional theory with the Perdew-Wang 91 exchange-correlation functional.

Gutowski, Maciej; Jaffe, John E.; Liu, Chun-Li; Stoker, Matt; Hegde, Rama I.; Rai, Raghaw S.; Tobin, Philip J.

2002-03-01

44

Reliability of Low-Temperature-Processing Hafnium Oxide Gate Dielectrics Prepared by Cost-Effective Nitric Acid Oxidation Technique  

Microsoft Academic Search

In this paper, the physical and electrical characteristics of low-temperature-processing hafnium oxide (HfO2) films are studied. A simple cost-effective room-temperature process was introduced to prepare high-k HfO2 dielectrics. A novel technique of direct oxidation of an ultrathin Hf metal by nitric acid, followed by rapid thermal annealing in N2 is demonstrated. The prepared HfO2 gate dielectrics show good uniformity, low

Chia-Hua Chang; Jenn-Gwo Hwu

2007-01-01

45

Thermal annealing effects on the structural and electrical properties of HfO2\\/Al2O3 gate dielectric stacks grown by atomic layer deposition on Si substrates  

Microsoft Academic Search

HfO2\\/Al2O3 gate dielectric thin film stacks were deposited on Si wafers using the atomic layer deposition technique. A 3.3-nm-thick Al2O3 interlayer was grown at 400 °C using Al(CH3)3 and O3, and 2.5-3.5-nm-thick HfO2 films were grown at either 300 or 400 °C using HfCl4 and H2O. Thermal annealing of the dielectric film stack at temperatures ranging from 400 to 1000

Moonju Cho; Hong Bae Park; Cheol Seong Hwang; Jong-Cheol Lee; Se-Jung Oh; Jaehack Jeong; Kwang Soo Hyun; Hee-Sung Kang; Young-Wuk Kim; Jong-Ho Lee

2003-01-01

46

Thickness Variation of HfO2 Films Under Post-Deposition Annealing Investigated By X-ray Reflectivity and X-ray Photoelectron Spectroscopy  

NASA Astrophysics Data System (ADS)

As transistor feature sizes scaling down, the ultra-thin HfO2 high-k dielectric has been used to replace SiO2 for the gate dielectric to meet a better EOT for good electric performances. X-ray Reflectivity (XRR) is an accurate instrument to analyze the ultra-thin HfO2 films based on an appropriate material structure model in the data analysis. However, the material structure model is not easily defined for the ultra-thin HfO2 films, especially when interfaces between layers are changed under thermal annealing. In this work, the interfaces between layers of the ultra-thin HfO2 films were investigated at the as-deposited condition (ASD) and post-deposition annealing (PDA) processes. X-ray Photoelectron Spectroscopy (XPS) was used to evaluate the layer structures, which were post-annealed up to 1000 °C using furnaces in the Ar ambiances. The experimental results and analysis showed that layer thicknesses, crystal phases and chemical structures of the ultra-thin HfO2 films were significantly dependent on annealing temperatures. Accordingly, the interface with increasing annealing temperatures was broadened due to the existence of HfSixOy. As a result, a four-layer material structure model of HfO2 (low-density)/HfO2/HfSixOy/SiO2/Si-substrate based on XPS analysis was constructed to significantly improve the XRR fitting process with genetic algorithm (GA). The structure analysis of the XRR spectra using the modified material structure model from the XPS analysis confirmed the interfacial broadening induced by the post-deposition annealing.

Chang, Yong-Qing; Fu, Wei-En

2011-11-01

47

Characterization of HfO2/Al2O3 gate dielectric nanometer-stacks grown by atomic layer deposition on Ge substrates  

NASA Astrophysics Data System (ADS)

We report the characteristics of HfO2/Al2O3 gate dielectric nanometer-stacks deposited on Ge substrates at 250 °C by atomic layer deposition using Hf[N(CH3)(C2H5)]4 and Al(CH3)3 as the precursors. The annealing effect on the interface and electrical properties of stack films was investigated by X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and electrical measurements. It is demonstrated that the regrowth of GeOx during annealing is suppressed by Al2O3 layer. And the annealed samples exhibit better electrical properties with reduction hysteresis, high capacitance value and improved leakage current density.

Li, Xue-Fei; Li, Ai-Dong; Qian, Xu; Fu, Ying-Ying; Wu, Di

2012-09-01

48

Effects of plasma nitridation of Al2O3 interlayer on thermal stability, fixed charge density, and interfacial trap states of HfO2 gate dielectric films grown by atomic layer deposition  

Microsoft Academic Search

HfO2\\/Al2O3 gate dielectric thin-film stacks were deposited on Si wafers using an atomic-layer-deposition technique. A 2.3-nm-thick Al2O3 interlayer was grown at 450 °C using Al(CH3)3 and O3, and (4-5)-nm-thick HfO2 films were grown at 400 °C using HfCl4 and H2O as precursors. Because the Al2O3 interlayer was not an effective Si-diffusion barrier layer on its own, the Al2O3 interlayer was

Hong Bae Park; Moonju Cho; Cheol Seong Hwang; Jong-Cheol Lee; Se-Jung Oh

2003-01-01

49

Effect of thickness on the crystallization of ultrathin HfSiON gate dielectrics  

NASA Astrophysics Data System (ADS)

The crystallization of ultrathin hafnium silicon oxynitride (HfSiON) gate dielectric is studied as a function of physical thickness. Grazing incidence x-ray diffraction (GI-XRD) was used to detect phase separation and crystallization of 1.5, 2.0, 2.5, and 4.0 nm HfSiON films after 1000 °C 10 s dopant activation anneal. Crystallization peaks corresponding to monoclinic and tetragonal HfO2 were detected in 2.5 and 4.0 nm HfSiON films. These GI-XRD results were supported by plan-view transmission electron microscopy images of the HfSiON films. Film crystallinity seems to impact voltage instability in thicker HfSiON films.

Pant, G.; Gnade, A.; Kim, M. J.; Wallace, R. M.; Gnade, B. E.; Quevedo-Lopez, M. A.; Kirsch, P. D.

2006-01-01

50

Interlayer-related paramagnetic defects in stacks of ultrathin layers of SiOx, Al2O3, ZrO2, and HfO2 on (100)Si  

Microsoft Academic Search

An electron spin resonance (ESR) study has been carried out of the influence of postdeposition heating on stacks of (100)Si with nanometer-thick dielectric layers of SiOx and atomic-layer-deposited Al2O3, ZrO2, and HfO2. This reveals upon postdeposition oxidation (PDO) in the range 650-800 °C the appearance of various SiO2-characteristic defects, including E', EX, and a 95-G doublet, in different intensities with

A. Stesmans; V. V. Afanas'ev

2005-01-01

51

Improved electrical properties of Ge metal-oxide-semiconductor capacitors with high-k HfO2 gate dielectric by using La2O3 interlayer sputtered with/without N2 ambient  

NASA Astrophysics Data System (ADS)

The electrical properties of n-Ge metal-oxide-semiconductor (MOS) capacitors with HfO2/LaON or HfO2/La2O3 stacked gate dielectric (LaON or La2O3 as interlayer) are investigated. It is found that better electrical performances, including lower interface-state density, smaller gate leakage current, smaller capacitance equivalent thickness, larger k value, and negligible C-V frequency dispersion, can be achieved for the MOS device with LaON interlayer. The involved mechanism lies in that the LaON interlayer can effectively block the interdiffusions of Ge, O, and Hf, thus suppressing the growth of unstable GeOx interlayer and improving the dielectric/Ge interface quality.

Xu, H. X.; Xu, J. P.; Li, C. X.; Lai, P. T.

2010-07-01

52

Effects of interfacial oxide layers of the electrode metals on the electrical characteristics of organic thin-film transistors with HfO2 gate dielectric  

Microsoft Academic Search

HfO2-based devices employing various electrode metals (Al, W, Pt, Cu, and Cr) were fabricated and characterized in order to examine the importance of the choice of metal electrode when sputter-depositing HfO2 films. It was found that metal-insulator-metal capacitors with an Al bottom electrode exhibit a significantly smaller leakage current and a larger breakdown field strength than devices using W, Pt,

W. M. Tang; M. T. Greiner; M. G. Helander; Z. H. Lu; W. T. Ng

2011-01-01

53

Application of deposited by ALD HfO2 and Al2O3 layers in double-gate dielectric stacks for non-volatile semiconductor memory (NVSM) devices  

NASA Astrophysics Data System (ADS)

The feasibility of the application of double-gate dielectric stacks with fabricated by atomic layer deposited (ALD) HfO2 and Al2O3 layers in non-volatile semiconductor memory (NVSM) devices was investigated. Significant improvement in retention at elevated temperatures after the application of ALD high-k oxides was demonstrated. Superior memory window (extrapolated at 10 years) of flat-band voltage (Ufb) value of the order of 2.6 V and 4.55 V at 85 °C, for stack with HfO2 and Al2O3, respectively, was obtained. Moreover, the analysis of conduction mechanisms in the investigated stacks under negative voltage revealed F-N tunneling in the range of high values of electric field intensity and lowering of barrier height with increasing temperature.

Mroczy?ski, Robert; Taube, Andrzej; Giera?towska, Sylwia; Guziewicz, El?bieta; Godlewski, Marek

2012-08-01

54

The effect of La2O3-incorporation in HfO2 dielectrics on Ge substrate by atomic layer deposition  

NASA Astrophysics Data System (ADS)

We compared the electrical properties of HfO2, HfO2/La2O3, and La-doped HfO2 gate insulators deposited on Ge substrate using an atomic layer deposition (ALD) process. TDMAH [tetrakis(dimethylamino)hafnium] and La(iprCp)3 [tris(isopropyl-cyclopentadienyl) lanthanum] were employed as Hf and La precursors, respectively. Chemical compositions and binding structures were analyzed by X-ray photoelectron spectroscopy (XPS). Electrical properties were evaluated by capacitance-voltage (C-V) and current-voltage (I-V) measurements. We found that incorporation of La2O3 near Ge can enhance the electrical properties of Ge MOS capacitors. The best electrical properties of 50 mV of hysteresis and mid ˜1012 cm-2 eV-1 range interface states were found for the 400 °C-annealed HfO2/La2O3 bilayer sample. These values are significantly better than those of ALD HfO2 gate insulators on Ge. We attribute this to the formation of LaGeOx layers on the Ge surface, which reduces GeO bonding.

Oh, Il-kwon; Kim, Min-Kyu; Lee, Jae-seung; Lee, Chang-Wan; Lansalot-Matras, Clement; Noh, Wontae; Park, Jusang; Noori, Atif; Thompson, David; Chu, Schubert; Maeng, W. J.; Kim, Hyungjun

2013-12-01

55

Investigation of HfO2 high-k dielectrics electronic structure on SiO2/Si substrate by x-ray photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

In this Letter, x-ray photoelectron spectroscopy (XPS) was used to investigate electronic structures of HfO2 with various thicknesses on SiO2/Si substrate prepared by atomic layer deposition with post deposition annealing of 600 °C, which is compatible with a gate last process in the fabrication of complementary metal oxide semiconductor. The hafnium silicate formed between HfO2 and SiO2 interface plays a key role in generating an internal electric field. This can be attributed to the presence of oxygen vacancies (Vo) at the interface. The XPS binding energy shifts of O 1s, Si 2p, and Hf 4f spectra with increasing HfO2 thicknesses can be explained by the presence of the internal field and differential charging effects. Electrical measurements of capacitor structures support the XPS result.

Duan, T. L.; Yu, H. Y.; Wu, L.; Wang, Z. R.; Foo, Y. L.; Pan, J. S.

2011-07-01

56

Controllable nitrogen incorporation in HfO2 films by modulating capacitively-combined inductively-coupled plasmas  

NASA Astrophysics Data System (ADS)

Capacitively-combined inductively-coupled nitrogen (N) plasma discharges were investigated to nitridize ultrathin HfO2 films (5 nm) for leakage improvement. The result of x-ray photoelectron spectroscopy analysis shows N incorporation into the HfO2 films. In terms of the plasma chemical and surface processes, nitridation samples show great improvements in surface structure and the leakage current property (it decreases from 4.6 × 10-4 to 2.1 × 10-7 A cm-2), while the leakage current is independent of the morphology. The radical concentration of N atoms increases with inductively-coupled plasma (ICP) power. This kind of capacitively-coupled plasma (CCP) combined with ICP modes is capable of modulating the electron energy probability functions (EEPFs) based on the power levels of ICP and can facilitate tuning of the N2 discharge dissociation characteristics. By modulating the EEPFs depending on the power levels of CCP and ICP, the radical concentration of the N atom increases by the electron-neutrals collision dependence on the high-energy electron, resulting in more N atoms incorporated in HfO2 films. The lower effective electron temperature and ion energy were obtained with ICP power, causing less film surface damage. Therefore, N atoms possess intrinsic effects that drastically reduce the electron leakage current through HfO2 dielectrics by deactivating the oxygen vacancy related gap states.

Jin, C. G.; Yang, Y.; Zhang, H. Y.; Huang, T. Y.; Wu, M. Z.; Zhuge, L. J.; Wu, X. M.; Ye, C.

2013-12-01

57

Interfacial self-cleaning in atomic layer deposition of HfO2 gate dielectric on In0.15Ga0.85As  

NASA Astrophysics Data System (ADS)

An interfacial self-cleaning phenomenon was found in the atomic layer deposition of HfO2 on In0.15Ga0.85As/GaAs substrate using Hf(NCH3C2H5)4, i.e., TEMAH, and H2O as the precursors. The native oxides of InGaAs were all satisfactorily removed from the interface through ligand exchange (substitution) reactions with the TEMAH precursor. It relieves the Fermi-level pinning in the HfO2/InGaAs heterostructure, as verified by the clear transition from accumulation to depletion in high-frequency capacitance-voltage relations and inversion in quasistatic measurement. A very low leakage current was also found from the metal-oxide-semiconductor capacitors of Au/Ti/HfO2/InGaAs.

Chang, C.-H.; Chiou, Y.-K.; Chang, Y.-C.; Lee, K.-Y.; Lin, T.-D.; Wu, T.-B.; Hong, M.; Kwo, J.

2006-12-01

58

Characterization of high- k gate dielectric films using SIMS  

NASA Astrophysics Data System (ADS)

Recently, the high- k materials (Al 2O 3, Ta 2O 5, HfO 2, ZrO 2,…,etc.), which are alternative dielectrics to silicon dioxide for memory and logic devices, come into notice. We have applied SIMS to the characterization of the ultra-thin HfO 2 films. SIMS with low energy primary ion has proven to be a beneficial technique to see depth profiles of impurities and their behaviors due to annealing. As for Si substrate without native oxide, Si diffusion as well as the formation of amorphous Hf xSi 1- xO y layer at HfO 2/Si interface seem to occur during growth of HfO 2 film, which has been confirmed by SIMS and other analytical techniques. Furthermore, it is found that ion yield of carbon in HfO 2 is larger than that in SiO 2 by more than two orders of magnitude.

Yamamoto, T.; Morita, N.; Sugiyama, N.; Karen, A.; Okuno, K.

2003-01-01

59

Performance enhancement of metal-oxide-semiconductor tunneling temperature sensors with nanoscale oxides by employing ultrathin Al2O3 high-k dielectrics  

NASA Astrophysics Data System (ADS)

We demonstrated a promising route for enhancing temperature sensitivity, improving saturation voltage, and reducing power consumption of the MOS(p) tunneling temperature sensors by introducing ultrathin Al2O3 into the dielectric stacks. Detailed illustrations of the working mechanism and device concept are given in this work. Three kinds of MOS(p) tunneling temperature sensors with nanoscale SiO2, HfO2, and Al2O3 dielectrics were compared comprehensively. For Al2O3 MOS(p) devices with an equivalent oxide thickness of 2 nm, the sensing performance was effectively improved and the temperature-sensitive current-voltage characteristics are reliable and reproducible. The low-temperature processing Al2O3 MOS(p) tunneling temperature sensors are potential candidates for temperature monitoring sensors on chips or biomedical systems under low thermal budget processing consideration.

Lin, Chien-Chih; Hwu, Jenn-Gwo

2013-08-01

60

In0.53Ga0.47As FinFETs with self-aligned molybdenum contacts and HfO2/Al2O3 gate dielectric  

NASA Astrophysics Data System (ADS)

InGaAs channel FinFETs with self-aligned molybdenum (Mo) contacts was demonstrated using a gate-last process. By realizing Mo contacts on in situ doped n++ InGaAs source and drain and self-aligned to channel, the FinFETs achieved series resistance of ˜250 ? ?m, which is the lowest value reported-to-date for InGaAs non-planar n-MOSFETs. A FinFET with channel length of 500 nm and equivalent oxide thickness (EOT) of 3 nm has an on-state/off-state current ratio of ˜105 and peak extrinsic transconductance of 255 ?S/?m at drain voltage of 0.5 V. To further reduce EOT, atomic-layer-deposited HfO2/Al2O3 high-k dielectric was integrated in InGaAs FinFETs. Good interface quality and small EOT of ˜1 nm were achieved. Forming gas annealing (FGA) was used for drive current enhancement. A 300 °C 30 min FGA leads to ˜48% increase in drive current as well as significant reduction of subthreshold swing, probably due to an improvement of the HfO2/Al2O3/InGaAs interface quality.

Zhang, Xingui; Guo, Hua Xin; Zhu, Zhu; Gong, Xiao; Yeo, Yee-Chia

2013-06-01

61

Low-frequency noise in Si 0.7Ge 0.3 surface channel pMOSFETs with ALD HfO 2/Al 2O 3 gate dielectrics  

NASA Astrophysics Data System (ADS)

Low-frequency noise was characterized in Si 0.7Ge 0.3 surface channel pMOSFETs with ALD Al 2O 3/HfO 2/Al 2O 3 stacks as gate dielectrics. The influences of surface treatment prior to ALD processing and thickness of the Al 2O 3 layer at the channel interface were investigated. The noise was of the 1/ f type and could be modeled as a sum of a Hooge mobility fluctuation noise component and a number fluctuation noise component. Mobility fluctuation noise dominated the 1/ f noise in strong inversion, but the number fluctuation noise component, mainly originating from traps in HfO 2, also contributed closer to threshold and in weak inversion. The number fluctuation noise component was negligibly small in a device with a 2 nm thick Al 2O 3 layer at the SiGe channel interface, which reduced the average 1/ f noise by a factor of two and decreased the device-to-device variations.

von Haartman, M.; Wu, D.; Malm, B. G.; Hellström, P.-E.; Zhang, S.-L.; Östling, M.

2004-12-01

62

Optimization of HfO2 films for high transconductance back gated graphene transistors  

NASA Astrophysics Data System (ADS)

Hafnium dioxide (HfO2) films, deposited using electron beam evaporation, are optimized for high performance back-gated graphene transistors. Bilayer graphene is identified on HfO2/Si substrate using optical microscope and subsequently confirmed with Raman spectroscopy. Back-gated graphene transistor, with 32 nm thick HfO2 gate dielectric, has been fabricated with very high transconductance value of 60 ?S. From the hysteresis of the current-voltage characteristics, we estimate the trap density in HfO2 to be in the mid 1011/cm2 range, comparable to SiO2.

Lakshmi Ganapathi, Kolla; Bhat, Navakanta; Mohan, Sangeneni

2013-08-01

63

Percolation path and dielectric-breakdown-induced-epitaxy evolution during ultrathin gate dielectric breakdown transient  

Microsoft Academic Search

A physical model has been developed which complies with the experimental observation on the failure mechanism of ultrathin gate oxide breakdown during constant voltage stress. Dynamic equilibrium needs to be established between the percolation conductive path and the dielectric breakdown induced epitaxy (DBIE) formation during gate dielectric breakdown transient. The model is capable of linking the percolation model, soft breakdown,

Chih Hang Tung; Kin Leong Pey; Lei Jun Tang; M. K. Radhakrishnan; Wen He Lin; Felix Palumbo; Salvatore Lombardo

2003-01-01

64

Thermal stability of HfO2 nanotube arrays  

SciTech Connect

Thermal stability of highly ordered hafnium oxide (HfO2) nanotube arrays prepared through an electrochemical anodization method in the presence of ammonium fluoride is investigated in a temperature range of room temperature to 900 C in flowing argon atmosphere. The formation of the HfO2 nanotube arrays was monitored by current density transient characteristics during anodization of hafnium metal foil. Morphologies of the as-grown and post-annealed HfO2 nanotube arrays were analyzed by powder Xray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Although monoclinic HfO2 is thermally stable up to 2000K in bulk, the morphology of HfO2 nanotube arrays degraded at 900 C. A detailed X-ray photoelectron spectroscopy (XPS) study revealed that the thermal treatment significantly impacted the composition and the chemical environment of the core elements (Hf and O), as well as F content coming from the electrolyte. Possible reasons for the degradation of the nanotube at high temperature were discussed based on XPS study and possible future improvements have also been suggested. Moreover, dielectric measurements were carried out on both the as-grown amorphous film and 500 C post-annealed crystalline film. This study will help us to understand the temperature impact on the morphology of nanotube arrays, which is important to its further applications at elevated temperatures.

Qiu, Xiaofeng [ORNL; Howe, Jane Y [ORNL; Meyer III, Harry M [ORNL; Tuncer, Enis [ORNL; Paranthaman, Mariappan Parans [ORNL

2010-01-01

65

Impact of electrical stress on the electrical characteristics of 2 MeV electron irradiated metal-oxide-silicon capacitors with atomic layer deposited Al2O3, HfO2 and nanolaminated dielectrics  

NASA Astrophysics Data System (ADS)

In this work, the impact of electrical stress on the electrical characteristics of 2 MeV electron irradiated metal-oxide-silicon capacitors with atomic layer deposited (ALD) high permittivity (high-k) dielectric layers of Al2O3, HfO2 and a nanolaminate of them is evaluated. The aim is to investigate the susceptibility to electrical stress of the radiation effects created in irradiated MOS structures, paying especial attention to any possible interaction between the radiation-induced damage and the subsequent electrical stress degradation. For this study, MOS capacitors with a nominal dielectric physical thickness of 10 nm (equivalent oxide thickness (EOT) between 3 nm and 7 nm) on different p-type and n-type silicon substrates were investigated. An exponentially increasing stress current was forced to flow in accumulation through the different dielectric layers, registering the evolution of gate voltage versus stress time until dielectric breakdown occurred. Capacitance-voltage characteristics of the different irradiated and non-irradiated structures are analyzed as a function of electrical stress. Different charge trapping behaviors and significant polarity dependence in interface state generation are observed for the dielectric layers subjected to substrate and gate injections. No clear interaction between radiation and electrical stress damages is noticed under substrate injection (n-type samples). However, higher negative charge trapping near the metal/dielectric interface is registered for the irradiated Al2O3 and nanolaminate layers subjected to gate injection and, in the case of the most irradiated samples, the radiation-induced interface states damage is found to dominate against the damage generated in early stages of the electrical stress.

Rafí, J. M.; González, M. B.; Takakura, K.; Tsunoda, I.; Yoneoka, M.; Beldarrain, O.; Zabala, M.; Campabadal, F.

2013-11-01

66

High damage threshold mirrors and polarizers in the ZrO2/SiO2 and HfO2/SiO2 dielectric systems  

NASA Astrophysics Data System (ADS)

The Phebus neodymium glass laser system located at Centre d'Etudes de Limeil Valenton (CEL-V) is the most powerful in Europe (20 kJ, 1 ns at (lambda) equals 10 53 nm and up to 8 kJ, 1 ns at (lambda) equals 351 nm). A major concern in the design of this system was the damage thresholds of the 1 meter diameter turning mirrors and of the large polarizers (0.3 m2). Matra Defense SA, in a joint effort with CEL-V, using the well known reactive e- beam process, has investigated and produced a new generation of efficient ZrO2/SiO2 and HfO2/SiO2 high-reflective and polarizing coatings, leading to a very high laser- conditioned damage thresholds. In addition to good flatness figures ((lambda) /4 to (lambda) /10 at He-Ne wavelength), excellent roughness values (5 - 10 A RMS) and excellent spectral characteristics, laser-conditioned damage thresholds were in the range of 25 - 30 J/cm2 and 12 - 15 J/cm2 respectively for mirrors and polarizers at 1.064 micrometers wavelength for a 3 ns pulse. Such performances are respectively 2 and 6 times higher than those of same components in the TiO2/SiO2 conventional design. Laser-conditioning effect, enhancing the damage threshold by at least a factor of 2, was observed as a durable improvement.

Fournet, Carine; Pinot, B.; Geenen, B.; Ollivier, F.; Alexandre, W.; Floch, Herve G.; Roussel, Andre; Cordillot, C.; Billon, D.

1992-07-01

67

High density and program-erasable metal-insulator-silicon capacitor with a dielectric structure of SiO2/HfO2-Al2O3 nanolaminate/Al2O3  

NASA Astrophysics Data System (ADS)

We demonstrate a program-erasable metal-insulator-silicon capacitor with a dielectric structure of SiO2/HfO2-Al2O3 nanolaminate (HAN)/Al2O3. The memory capacitor exhibits a high capacitance density of 4.5 fF/?m2, a large memory window of 1.45 V in the case of +12 V program/-12 V erase for 5 ms, nearly symmetrical positive and negative flatband voltages under the program/erase operations with the same magnitudes of voltage and time, and no erase saturation. This is attributed to the fact that the introduction of atomic-layer-deposited high-dielectric-constant HAN/Al2O3 layers increases the electric field across the tunnel oxide and reduces that across the blocking layer, hence, preventing effectively Fowler-Nordheim tunneling current through the blocking layer. Additionally, we find that the HAN is a promising charge storage layer with sufficient trapping centers for electrons and holes.

Ding, Shi-Jin; Zhang, Min; Chen, Wei; Zhang, David Wei; Wang, Li-Kang; Wang, X. P.; Zhu, Chunxiang; Li, Ming-Fu

2006-01-01

68

Two-step annealing effects on ultrathin EOT higher-k (k = 40) ALD-HfO2 gate stacks  

NASA Astrophysics Data System (ADS)

Ultrathin HfO2 gate stacks with very high permittivity were fabricated by atomic layer deposition (ALD) and a novel two-step post-deposition annealing (PDA) technique. First, a no-cap pre-crystallization anneal degasses residual contaminations in the ALD layer, and second, a Ti-cap anneal enhances the permittivity of HfO2 by generating a cubic crystal phase. The Ti-cap layer simultaneously suppresses growth of interfacial SiO2 during annealing by absorbing residual oxygen released from HfO2. Using these techniques, the dielectric constant of the ALD-HfO2 could be enhanced to 40 for 2.4-4.0 nm HfO2 thickness.

Morita, Yukinori; Migita, Shinji; Mizubayashi, Wataru; Masahara, Meishoku; Ota, Hiroyuki

2013-06-01

69

Effect of ion implantation energy for the synthesis of Ge nanocrystals in SiN films with HfO2/SiO2 stack tunnel dielectrics for memory application  

PubMed Central

Ge nanocrystals (Ge-NCs) embedded in SiN dielectrics with HfO2/SiO2 stack tunnel dielectrics were synthesized by utilizing low-energy (?5 keV) ion implantation method followed by conventional thermal annealing at 800°C, the key variable being Ge+ ion implantation energy. Two different energies (3 and 5 keV) have been chosen for the evolution of Ge-NCs, which have been found to possess significant changes in structural and chemical properties of the Ge+-implanted dielectric films, and well reflected in the charge storage properties of the Al/SiN/Ge-NC + SiN/HfO2/SiO2/Si metal-insulator-semiconductor (MIS) memory structures. No Ge-NC was detected with a lower implantation energy of 3 keV at a dose of 1.5 × 1016 cm-2, whereas a well-defined 2D-array of nearly spherical and well-separated Ge-NCs within the SiN matrix was observed for the higher-energy-implanted (5 keV) sample for the same implanted dose. The MIS memory structures implanted with 5 keV exhibits better charge storage and retention characteristics compared to the low-energy-implanted sample, indicating that the charge storage is predominantly in Ge-NCs in the memory capacitor. A significant memory window of 3.95 V has been observed under the low operating voltage of ± 6 V with good retention properties, indicating the feasibility of these stack structures for low operating voltage, non-volatile memory devices.

2011-01-01

70

Dispersion control over the ultraviolet-visible-near-infrared spectral range with HfO2\\/SiO2-chirped dielectric multilayers  

Microsoft Academic Search

We report the first realization, to the best of our knowledge, of a chirped multilayer dielectric mirror providing dispersion control over the spectral range of 300-900 nm and the first use of hafnium oxide in a chirped mirror. The technology opens the door to the reliable and reproducible generation of monocycle laser pulses in the blue-violet spectral range, will benefit

V. Pervak; F. Krausz; A. Apolonski

2007-01-01

71

Development of Nitrous Oxide-Based Ultrathin Gate and Tunnel Dielectrics for MOS Devices  

Microsoft Academic Search

The use of ultrathin dielectric in the ULSI (Ultra -Large Scale Itegration) era is curcial for device functionality and reliability. However, it is well known that conventional thermally grown pure oxides in the ultra-thin regime (40 -60A) do not provide adequate electrical and reliability characteristics. The use of N_2O gas in oxidation produces oxides (oxynitrides) with better dielectric integrity, lower

Ka-Fai Lai

1995-01-01

72

Reversible creation and annihilation of a local leakage path in HfO2/GeOx stacked gate dielectrics: A direct observation by ultrahigh vacuum conducting atomic force microscopy  

NASA Astrophysics Data System (ADS)

By direct observation using ultrahigh vacuum conducting atomic force microscopy, it is found that a local leakage path in HfO2/GeOx stacks created by an electrical stress with a positive tip bias annihilates after applying a reverse tip bias. The creation and annihilation of these paths are repeatable without noticeable degradation. The fact that these paths annihilate by a very small reverse bias suggests that this behavior is caused by local reduction and oxidation in the HfO2 layer.

Yamamura, K.; Kita, K.; Toriumi, A.; Kyuno, K.

2006-11-01

73

A Non-Aging Screen to Prevent Wearout of Ultra-Thin Dielectrics  

Microsoft Academic Search

As MOS gate dielectrics are scaled to thinner dimensions, lognormal statistics determine the limit at which aging screens are no longer effective in reducing the time-dependent failure rate of dielectric breakdown. This paper presents an alternative non-aging reliability screen as applied to ultra-thin DRAM storage gate dielectrics. Early breakdown is correlated with increased dielectric leakage current, which can be detected

William K. Meyer; Dwight L. Crook

1985-01-01

74

Low-voltage pentacene field-effect transistors with ultrathin polymer gate dielectrics  

NASA Astrophysics Data System (ADS)

Organic field-effect transistors (OFETs) for low-voltage operation have been realized with conventional polymer gate dielectrics such as polyimides and cross-linked poly-4-vinyl phenols (PVPs) by fabricating ultrathin films. These ultrathin polymers (thickness ~10 nm) have shown good insulating properties, including high breakdown fields (>2.5 MV/cm). With ultrathin dielectrics, high capacitances (>250 nF/cm2) have been achieved, allowing operation of OFETs within -3 V. Pentacene OFETs with ultrathin PVP dielectrics exhibit a mobility of 0.5 cm2/V s, an on-off ratio of 105, and a small subthreshold swing of 174 mV/decade when devices are operated at -3 V.

Yang, Sang Yoon; Kim, Se Hyun; Shin, Kwonwoo; Jeon, Hayoung; Park, Chan Eon

2006-04-01

75

Plasmonic excitations in ultrathin metal films on dielectric substrates  

NASA Astrophysics Data System (ADS)

The optical properties of metals are mainly determined by their plasmonic excitations, with various intriguing phenomena associated with systems in reduced dimensions. In this paper, we present a systematic study of the plasmonic excitations in ultrathin metal films on dielectric substrates using two different theoretical approaches, and with Mg thin films on Si as prototype systems. The bulk of the results are obtained using the first approach within first-principles time-dependent local density approximation. We show that the presence of the substrate substantially modifies the plasmon hybridization of the metal films; in turn, the plasmon excitation in the films strongly enhances the absorption of the substrate. The detailed absorption spectra contain several intriguing features. Above the Mg surface plasmon mode, we observe a broad resonance due to the hybridization between the antisymmetric surface plasmon and multipole surface plasmon. Furthermore, below the Mg surface plasmon mode, there also exists a broad absorption feature, caused by individual electron–hole pair excitations. In the second approach, we use a semi-classical local optics model to reveal an intrinsic connection between the broad absorption feature and the multipole surface plasmon modes, which result from the single-particle and collective excitations of the same surface electrons, respectively. Our theoretical predictions on the plasmon dispersions and absorption spectra are also shown to be qualitatively consistent with the latest experimental observations using electron energy loss spectroscopy for Mg thin films grown on Si substrates.

Li, Xiaoguang; Teng, Ao; Özer, Mustafa M.; Shen, Jian; Weitering, Hanno H.; Zhang, Zhenyu

2014-06-01

76

Electrical properties and thermal stability of CVD HfOxNy gate dielectric with poly-Si gate electrode  

Microsoft Academic Search

High-quality, ultrathin chemical vapor deposition (CVD) hafnium oxynitride (HfOxNy) gate dielectric with poly-silicon (Si) gate electrode has been investigated for the first time. This CVD HfOxNy gate dielectric film remains amorphous after 950 °C N2 annealing. Compared with HfO2 films with poly-Si gate electrode and similar equivalent oxide thickness (EOT), CVD HfOxNy shows significantly reduction in leakage-current density and boron

C. H. Choi; T. S. Jeon; R. Clark; D. L. Kwong

2003-01-01

77

Atomic layer deposited ultra thin HfO2 and Al2O3 interfacial layers for high performance Dye Sensitized Solar Cells  

Microsoft Academic Search

This paper presents the possibility of improving the performance of dye sensitized solar cells (DSSCs) by treating the mesoporous TiO2 using ultra thin metal oxides such as hafnium oxide (HfO2) and aluminum oxide (Al2O3) grown by atomic layer deposition (ALD) method. Ultrathin HfO2 and Al2O3 (few nm in thickness) metal oxide layers affect the density and activity of the interface

Mariyappan Shanmugam; Mahdi Farrokh Baroughi; David Galipeau; Michal Ropp

2009-01-01

78

Permittivity increase of yttrium-doped HfO2 through structural phase transformation  

NASA Astrophysics Data System (ADS)

An approach to control the dielectric properties of hafnium-based oxide films with an intentional structural phase transformation was proposed and demonstrated. Yttrium serves effectively as a dopant to induce a phase transformation from the monoclinic to the cubic phase even at 600 °C. The yttrium-doped HfO2 films show higher permittivity than undoped HfO2, and the permittivity as high as 27 is obtained by 4 at. % yttrium doping. The permittivity enhancement by yttrium doping can be explained by the shrinkage of molar volume due to the structural phase transformation. The advantage of yttrium doping is more pronounced at higher temperatures, since the permittivity of undoped HfO2 is reduced significantly, whereas that of 17 at. % yttrium-doped film shows no change even at 1000 °C.

Kita, Koji; Kyuno, Kentaro; Toriumi, Akira

2005-03-01

79

Refractive index and dielectric constant evolution of ultra-thin gold from clusters to films  

Microsoft Academic Search

Using high-speed picometrology, the complete cluster-to-film dielectric trajectories of ultra-thin gold films on silica are measured at 488 nm and 532 nm wavelengths for increasing mass-equivalent thickness from 0.2 nm to 10 nm. The trajectories are parametric curves on the complex dielectric plane that consist of three distinct regimes with two turning points. The thinnest regime (0.2 nm - 0.6

X. F. Wang; K. P. Chen; M. Zhao; D. D. Nolte

2010-01-01

80

Structural, electronic, optical, elastic properties and Born effective charges of monoclinic HfO2 from first-principles calculations  

NASA Astrophysics Data System (ADS)

First-principles calculations of structural, electronic, optical, elastic, mechanical properties, and Born effective charges of monoclinic HfO2 are performed with the plane-wave pseudopotential technique based on the density-functional theory. The calculated structural properties are consistent with the previous theoretical and experimental results. The electronic structure reveals that monoclinic HfO2 has an indirect band gap. The analyses of density of states and Mulliken charges show mainly covalent nature in Hf-O bonds. Optical properties, including the dielectric function, refractive index, extinction coefficient, reflectivity, absorption coefficient, loss function, and optical conductivity each as a function of photon energy are calculated and show an optical anisotropy. Moreover, the independent elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson's ratio, compressibility, Lamé constant, sound velocity, Debye temperature, and Born effective charges of monoclinic HfO2 are obtained, which may help to understand monoclinic HfO2 for future work.

Liu, Qi-Jun; Zhang, Ning-Chao; Liu, Fu-Sheng; Liu, Zheng-Tang

2014-04-01

81

Gate quality ultrathin (2.5 nm) PECVD deposited oxynitride and nitrided oxide dielectrics  

Microsoft Academic Search

Ultrathin oxynitride using plasma assisted deposition was evaluated against thermal oxide and nitrided thermal oxide as an alternative direct tunneling gate dielectric to thermal oxide in the 2.5-nm regime. The oxynitride showed an enhanced high field effective mobility relative to the thermal oxide although the low field mobility was slightly depressed. The N2O nitrided oxide showed an enhanced high field

Effiong Ibok; Khaled Ahmed; Ming-Yin Hao; Bob Ogle; Jimmie J. Wortman; John R. Hauser

1999-01-01

82

Chemical states and electronic structure of a HfO2/Ge(001) interface  

NASA Astrophysics Data System (ADS)

We report the chemical bonding structure and valence band alignment at the HfO2/Ge(001) interface by systematically probing various core level spectra as well as valence band spectra using soft x rays at the Stanford Synchrotron Radiation Laboratory. We investigated the chemical bonding changes as a function of depth through the dielectric stack by taking a series of synchrotron photoemission spectra as we etched through the HfO2 film using a dilute hydrogen fluoride solution. We found that a very nonstoichiometric GeOx layer exists at the HfO2/Ge interface. The valence band spectra near the Fermi level in each different film structure were carefully analyzed, and as a result, the valence band offset between Ge and GeOx was determined to be ?Ev (Ge-GeOx)=2.2+/-0.15 eV, and that between Ge and HfO2, ?Ev (Ge-HfO2)=2.7+/-0.15 eV.

Seo, Kang-Ill; McIntyre, Paul C.; Sun, Shiyu; Lee, Dong-Ick; Pianetta, Piero; Saraswat, Krishna C.

2005-07-01

83

Terahertz surface plasmons excitation by nonlinear mixing of lasers in over ultrathin metal film coated dielectric  

NASA Astrophysics Data System (ADS)

An ultrathin metal film deposited on dielectric plate supports low loss THz surface plasma wave (SPW). The SPW field falls off away from the metal film both inside the dielectric as well as in free space. Two lasers normally incident, from free space on the planar structure, exert a difference frequency ponderomotive force on the free electrons of the film and resonantly excite THz SPW. The ratio of SPW amplitude to lasers is 10-3 at laser intensity of 3 × 1012 W/cm2 at 1 ? m wavelength. The growth rate falls monotonically because at higher frequency the coupling of SPW is weak.

Kumar, Pawan; Tripathi, V. K.

2013-08-01

84

Chemical and dielectrical characteristics of ultrathin oxides grown by atomic force microscopy and scanning electron beam  

SciTech Connect

We report a comparative study on the chemical and dielectrical properties of ultrathin oxides grown by atomic force microscopy (AFM) and scanning electron beam (SEB) techniques. Oxide grown by AFM (AFM oxide) shows preferential etching as compared to oxide grown by SEB (SEB oxide). The structural and chemical features of these oxides were probed using time-of-flight secondary ion mass spectrometry (TOF-SIMS) time profiling. It was found that AFM oxide is richer in Si-H and Si-OH content, while SEB oxide is oxygen rich and relatively dense in structure. The dielectric strength of AFM and SEB oxides were further evaluated by conducting AFM (c-AFM). The current-voltage characteristics and dielectric breakdown probability of these oxides were compared. The correlation between Si-H and Si-OH site formation and its impact on the chemical and dielectrical stability of AFM and SEB oxides was discussed.

Xie, X.N.; Chung, H.J.; Sow, C.H.; Wee, A.T.S. [NUS Nanoscience and Nanotechnology Initiative, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore and NUS Nanoscience and Nanotechnology Initiative, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore)

2005-05-09

85

ALD HfO2 using heavy water (D2O) for improved MOSFET stability  

Microsoft Academic Search

Device instability is one of the most challenging issues to implement high-k gate dielectrics. Incorporation of deuterium during the ALD (atomic layer deposition) process effectively improves the interface quality that enhances high-k device stability and reliability. Compared to H2O processed HfO2 devices, devices with D2O processing result in a significantly smaller Vt shift after constant voltage stressing at room temperature

H.-H. Tseng; M. E. Ramon; L. Hebert; P. J. Tobin; D. Triyoso; J. M. Grant; Z. X. Jiang; D. Roan; S. B. Samavedam; D. C. Gilmer; S. Kalpat; C. Hobbs; W. J. Taylor; O. Adetutu; B. E. White

2003-01-01

86

Observation of bulk HfO2 defects by spectroscopic ellipsometry  

Microsoft Academic Search

Spectroscopic ellipsometry was used to investigate the oxidation of pure Hf films on silicon for the formation of HfO2 (hafnium oxide) gate-dielectric films in advanced complementary metal-oxide-semiconductor field-effect transistors. Absorption coefficients near the absorption edge were extracted using the data inversion method, in which the optical constants for short wavelengths were calculated using the film thickness determined from long-wavelength data.

Hideki Takeuchi; Daewon Ha; Tsu-Jae King

2004-01-01

87

Computational investigation of the phase stability and the electronic properties for Gd-doped HfO2  

NASA Astrophysics Data System (ADS)

Rare earth doping is an important approach to improve the desired properties of high-k gate dielectric oxides. We have carried out a comprehensive theoretical investigation on the phase stability, band gap, formation of oxygen vacancies, and dielectric properties for the Gd-doped HfO2. Our calculated results indicate that the tetragonal phase is more stable than the monoclinic phase when the Gd doping concentration is greater than 15.5%, which is in a good agreement with the experimental observations. The dopant's geometric effect is mainly responsible for the phase stability. The Gd doping enlarges the band gap of the material. The dielectric constant for the Gd-doped HfO2 is in the range of 20-30 that is suitable for high-k dielectric applications. The neutral oxygen vacancy formation energy is 3.2 eV lower in the doped material than in pure HfO2. We explain the experimental observation on the decrease of photoluminescence intensities in the Gd-doped HfO2 according to forming the dopant-oxygen vacancy complexes.

Wang, L. G.; Xiong, Y.; Xiao, W.; Cheng, L.; Du, J.; Tu, H.; van de Walle, A.

2014-05-01

88

Structural, electronic and magnetic properties of the surfaces of tetragonal and cubic HfO2  

NASA Astrophysics Data System (ADS)

We present ab initio density-functional theory (DFT) calculations of the structure and stability of the monoclinic (m), tetragonal (t) and cubic (c) phases of HfO2 and of the stability and the structural, electronic, and magnetic properties of the polar (001) surface of t-HfO2 and the (100) and (111) surfaces of c-HfO2. We show that on all three surfaces, a termination by Hf leads to a metallic and non-magnetic surface, while surfaces covered by a full monolayer of O are predicted to be half-metallic and ferromagnetic, the magnetisms being induced by the Coulomb repulsion between p-holes in the O-2p valence band. In contrast, the partially reduced surfaces terminated by half a monolayer of oxygen are found to be insulating and non-magnetic. Ab initio statistical mechanics in combination with the DFT total-energy calculations show that the partially reduced surfaces are stable over the entire range of admissible values of the chemical potential of oxygen. Investigations of the formation of Hf vacancies on the Hf- and O-terminated surfaces of tetragonal HfO2 demonstrate that under oxidizing conditions, the formation of Hf subsurface vacancies is energetically favored on the partially reduced O-terminated surface. The formation of Hf vacancies causes the creation of holes in the O-2p valence band and of magnetic moments on the surrounding O atoms. That the formation of near-surface Hf vacancies on the O-terminated surface is energetically favored is in contrast to a high formation energy for neutral Hf vacancies in bulk HfO2 and suggests a cooperative mechanism between surface- and vacancy-formation. We discuss our findings in relation to recent reports on ferromagnetism in ultrathin HfO2 films and other models for the formation of p-wave ferromagnetism.

Beltrán, J. I.; Muñoz, M. C.; Hafner, J.

2008-06-01

89

Synthesis of Freestanding HfO2 Nanostructures.  

National Technical Information Service (NTIS)

Two new methods for synthesizing nanostructured HfO2 have been developed. The first method entails exposing HfTe2 powders to air. This simple process resulted in the formation of nanometer scale crystallites of HfO2. The second method involved a two-step ...

A. O'Shea J. Wallace K. Boyle L. Strauss T. Kidd

2011-01-01

90

Dielectric property and conduction mechanism of ultrathin zirconium oxide films  

NASA Astrophysics Data System (ADS)

Stoichiometric, uniform, amorphous ZrO2 films with an equivalent oxide thickness of ~1.5 nm and a dielectric constant of ~18 were deposited by an atomic layer controlled deposition process on silicon for potential applications in metal-oxide-semiconductor (MOS) devices. The conduction mechanism is identified as Schottky emission at low electric fields and as Poole-Frenkel emission at high electric fields. The MOS devices showed low leakage current, small hysteresis (<50 mV), and low interface state density (~2×1011 cm-2 eV-1). Microdiffraction and high-resolution transmission electron microscopy showed a localized monoclinic phase of ?-ZrO2 and an amorphous interfacial ZrSixOy layer which has a corresponding dielectric constant of 11.

Chang, J. P.; Lin, Y.-S.

2001-11-01

91

Dielectric properties of cobalt ferrite nanoparticles in ultrathin nanocomposite films.  

PubMed

Multilayered nanocomposite films (thickness 50-90 nm) of cobalt ferrite nanoparticles (np-CoFe2O4, 18 nm) were deposited on top of interdigitated microelectrodes by the layer-by-layer technique in order to study their dielectric properties. For that purpose, two different types of nanocomposite films were prepared by assembling np-CoFe2O4 either with poly(3,4-ethylenedioxy thiophene):poly(styrene sulfonic acid) or with polyaniline and sulfonated lignin. Despite the different film architectures, the morphology of both was dominated by densely-packed layers of nanoparticles surrounded by polyelectrolytes. The dominant effect of np-CoFe2O4 was also observed after impedance spectroscopy measurements, which revealed that dielectric behavior of the nanocomposites was largely influenced by the charge transport across nanoparticle-polyelectrolyte interfaces. For example, nanocomposites containing np-CoFe2O4 exhibited a single low-frequency relaxation process, with time constants exceeding 15 ms. At 1 kHz, the dielectric constant and the dissipation factor (tan ?) of these nanocomposites were 15 and 0.15, respectively. These values are substantially inferior to those reported for pressed pellets made exclusively of similar nanoparticles. Impedance data were further fitted with equivalent circuit models from which individual contributions of particle's bulk and interfaces to the charge transport within the nanocomposites could be evaluated. The present study evidences that such nanocomposites display a dielectric behavior dissimilar from that exhibited by their individual counterparts much likely due to enlarged nanoparticle-polyelectrolyte interfaces. PMID:24145704

Alcantara, Gustavo B; Paterno, Leonardo G; Fonseca, Fernando J; Pereira-da-Silva, Marcelo A; Morais, Paulo C; Soler, Maria A G

2013-12-01

92

Thermal behavior of hafnium-based ultrathin films on silicon  

NASA Astrophysics Data System (ADS)

We report here on the thermodynamical stability of ultrathin, hafnium-based dielectric films, namely hafnium oxide (HfO2), silicate (HfSixOy), and aluminum silicate (AlHfxSiyOz), deposited on silicon. These materials are promising candidates to replace the well established silicon oxide and oxynitride as gate dielectric materials in advanced Si-based complementary metal-oxide-semiconductor technology. Since there are mandatory requirements on the gate dielectric material, hafnium oxide is currently being modified, by adding silicon and aluminum into the matrix, increasing its thermal stability, and improving its electrical properties. Diffusion-reaction during thermal processing was investigated using isotopic substitution together with ion beam techniques such as Rutherford backscattering spectrometry, narrow nuclear resonance profiling, and nuclear reaction analysis. The chemical changes in the films were accessed by x-ray photoelectron spectroscopy.

Pezzi, R. P.; Morais, J.; Dahmen, S. R.; Bastos, K. P.; Miotti, L.; Soares, G. V.; Baumvol, I. J. R.; Freire, F. L.

2003-07-01

93

Ultrathin silicon nitride gate dielectrics prepared by catalytic chemical vapor deposition at low temperatures  

NASA Astrophysics Data System (ADS)

The feasibility of using ultrathin silicon nitride (SiNx) films, prepared by catalytic chemical vapor deposition (Cat-CVD) method, as an ultrathin gate dielectric is reported. The effects of postdeposition treatments carried out using hydrogen (H2)-decomposed species or NH3-decomposed species formed by catalytic cracking of H2 and NH3 are also studied. A small hysteresis loop is seen in the C-V curve of as-deposited Cat-CVD SiNx films. The leakage current in the case of these films with equivalent oxide thickness (EOT) of 3 nm is slightly larger than that in the conventional thermal SiO2 films of similar EOT. However, it is found that the properties of Cat-CVD SiNx films are markedly improved by the postdeposition H2 or NH3 treatments, that is, the hysteresis loop disappears and the leakage current decreases by three orders of magnitude.

Sato, Hidekazu; Izumi, Akira; Matsumura, Hideki

2000-10-01

94

Electrical characterization of few-layer MoS2 on HfO2 substrate  

NASA Astrophysics Data System (ADS)

Due to the realization of graphene transistors but without applicable bandgap, the similar layered structure molybdenum disulfide (MoS2) field effect transistors with nonzero bandgap have been demonstrated and reveal promising potential. Previous experiments showed that carrier mobility could be enhanced by depositing hafnium dioxide (HfO2) on top of MoS2 devices, which was possibly attribute to the suppression of Coulomb scattering by high-? environment and surface polar phonon scattering. In our talk, we will present the electrical transport experiments in few layers of MoS2 on HfO2 dielectrics, including the carrier mobility improvement and electrical transport phenomena in high bias region.

Kumar, Jatinder; Chien, Hui-Chun; Chiu, Hsin-Ying

2013-03-01

95

Development of Nitrous Oxide-Based Ultrathin Gate and Tunnel Dielectrics for MOS Devices.  

NASA Astrophysics Data System (ADS)

The use of ultrathin dielectric in the ULSI (Ultra -Large Scale Itegration) era is curcial for device functionality and reliability. However, it is well known that conventional thermally grown pure oxides in the ultra-thin regime (40 -60A) do not provide adequate electrical and reliability characteristics. The use of N_2O gas in oxidation produces oxides (oxynitrides) with better dielectric integrity, lower defect density, less boron penetration and better process control, etc.. The N _2O oxide is thus a better candidate for ultrathin oxide application. Pre-oxidation surface preparation by conventional RCA clean increases surface microroughness and provides no passivation to the wafer surface. A new cleaning method based on methanol/HF has been developed and show improvement in the dielectric integrity of both oxides and oxynitrides. A microscopic model is also proposed. The thickness dependent of stress-induced leakage current (SILC) was studied for pure oxides and N _2O oxides. A "turn around" effect was observed such that for thickness going down from ~ 50A, SILC actually decreases. This effect is modeled by the two-step trap-assisted tunneling model where trap generation rate and tunneling time constants are the determining factors for the SILC. Effects of oxide exposure, photoresist and gate dopant activation on the plasma damage immunity of ultrathin oxides were studied. It was found that not only charging damage and radiation damage are present during plasma exposure, photo-annealing by low energy UV light is competing with the damaging processes. The actual extent of damage depends on the plasma operating condition. It implies that using fully-covered MOSCAP structures is not an accurate indicator of the actual damage in integrated circuits. It was also found that photoresist quality affect plasma damage and patterning gate before ion implantation can reduce charging problem. Damage recovery effect of various RTA annealing processes is also studied. The effects of different gate dopant species, concentration and microstructure on the electrical and reliability characteristics of ultrathin oxides and N _2O oxynitrides are studied. Optimization of the gate doping level is based on poly depletion, charge -to-breakdown, and stress-induced leakage current. The optimization conditions for N+ and P+ gate are found to be very different.

Lai, Ka-Fai

96

Preparation and Properties of Thin HfO 2 Films  

Microsoft Academic Search

HfO2 layers were grown on silicon by metalorganic chemical vapor deposition using (C5H5)2Hf(CH3)2, (C5H5)2Hf(N(C2H5)2)2, and Hf(dpm)4 as volatile precursors and were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, and IR spectroscopy. The films were shown to consist of monoclinic HfO2 and to contain hafnium silicide and silicate at the HfO2\\/Si interface. The presence of hafnium silicide was attributed to oxygen

L. V. Yakovkina; V. N. Kichai; T. P. Smirnova; V. V. Kaichev; Yu. V. Shubin; N. B. Morozova; K. V. Zherikova; I. K. Igumenov

2005-01-01

97

Dielectric-breakdown-induced epitaxy: a universal breakdown defect in ultrathin gate dielectrics  

Microsoft Academic Search

The breakdown phenomena in SiOxNy (EOT=20 Å) gate dielectric under a two- stage constant voltage stress in inversion mode are physically analyzed with the aid of transmission electron microscopy. The results show that dielectric-breakdown-induced epitaxy (DBIE) remains as one of the major failure defects responsible for gate dielectric breakdown evolution even for a stress voltage as low as 2.5 V.

Thayalan A. L. Selvarajoo; Rakesh Ranjan; Kin-Leong Pey; Lei-Jun Tang; Chih Hang Tung; Wenhe Lin

2005-01-01

98

The chemical analysis about post annealing effect of HfO2 on Si-passivated GaAs  

NASA Astrophysics Data System (ADS)

In order to develop a high performance MOS device, 3-5 based semiconductors as a high carrier transport semiconductors have been seriously considered. Especially, GaAs with HfO2 as gate dielectric material attract as a candidate for future MOS FET device. Since, larger trap density at HfO2/GaAs interface than for HfO2/Si interface degrade device performance, Si interfacial layer was introduced to reduce interfacial trap. Moreover, Si reduces intrinsic defects at GaAs surface by reconstruct Ga or As homo bonds. In this study, we focused on changes in the chemical and structural characteristics of HfO2/Si/GaAs film as a function of post annealing temperature. The interfacial reactions induced by post annealing were investigated by XPS, REELS, and XAS. The results show that Si layer decrease the diffusion and oxide formation of Ga and As. Also, the post nitridation significantly improve the diffusion barrier by forming the Ga-N layer. XAS result also consists with the fact that the post nitridation suppress Ga diffusion. The band offsets between GaAs and high-k gate dielectric were aligned using XPS and REELS.

Park, Sang Han; Kim, Hyo Jin; Kim, Dae-Kyong; Cho, Mann-Ho; Kim, Chung Yi; Kim, Hyoungsub

2012-02-01

99

Improved interfacial and electrical properties of atomic layer deposition HfO2 films on Ge with La2O3 passivation  

NASA Astrophysics Data System (ADS)

We report the characteristics of HfO2 films deposited on Ge substrates with and without La2O3 passivation at 250 °C by atomic layer deposition (ALD) using La[N(SiMe3)2]3 and Hf[N(CH3)(C2H5)]4 as the precursors. The HfO2 is observed to form defective HfGeOx at its interface during 500 °C postdeposition annealing. The insertion of an ultrathin La2O3 interfacial passivation layer effectively prevents the Ge outdiffusion and improves interfacial and electrical properties. Capacitance equivalent thickness (CET) of 1.35 nm with leakage current density JA of 8.3 × 10-4 A/cm2 at Vg = 1 V is achieved for the HfO2/La2O3 gate stacks on Ge substrates.

Li, Xue-Fei; Liu, Xiao-Jie; Cao, Yan-Qiang; Li, Ai-Dong; Li, Hui; Wu, Di

2013-01-01

100

Thermal stability of HfO 2 nanotube arrays  

Microsoft Academic Search

Thermal stability of highly ordered hafnium oxide (HfO2) nanotube arrays prepared through an electrochemical anodization method in the presence of ammonium fluoride is investigated in a temperature range of room temperature to 900°C in flowing argon atmosphere. The formation of the HfO2 nanotube arrays was monitored by current density transient characteristics during anodization of hafnium metal foil. Morphologies of the

Xiaofeng Qiu; Jane Y. Howe; Harry M. Meyer; Enis Tuncer; M. Parans Paranthaman

2011-01-01

101

Characterization, engineering, and reliability of nano-scale high-k dielectrics and semiconductors interfaces  

NASA Astrophysics Data System (ADS)

The continued scaling of silicon complementary metal-oxide-semiconductor devices has lead to a need to replace the SiO2 gate insulator with high-k dielectric oxides, such as ZrO2 and HfO 2-based materials, to maintain a smaller leakage current without losing electrostatic gate control of the channel region. The main objectives of this dissertation are to understand the physical and electronic structure of the high-k/semiconductor interfaces, and based on that understanding, to develop new techniques that can modify or passivate the high-k /semiconductor interfaces for improved performance and reliability. First, we investigated chemical bonding structures and valence band alignments at the high-k (HfO2) and semiconductor (Si, Ge) interfaces using Synchrotron radiation photoemission spectroscopy. We found that highly non-stoichiometric GeOx exists at the HfO2/Ge interface, while stoichiometric SiOx was analyzed at the HfO 2/Si interface. From the valence band spectra the valence band offsets between HfO2 and Si or Ge were determined. Second, we demonstrated that the Zr-silicate interfacial layer (IL) can be formed between ZrO2 and a Si substrate by controlling the solid state reaction between Zr and an underlying SiO2/Si substrate. Incorporation of the metal-silicate layer improved the electrical properties, and reduced the stack equivalent oxide thickness. We also determined changes in chemical bonding at the HfO2/Si interface and associated electrical properties after the SiO2 IL is gettered by a Ti metal overlayer. We found that the removal of a part of SiO2 IL by oxygen-gettering Ti electrodes may be a promising approach for engineering ultrathin EOT without provoking a significant increase in interface trap density. Finally, for the first time, we developed a new technique to incorporate fluorine in high-k stack (HfO2/SiO2), and discovered that the negative bias temperature instability problems, such as positive charge trapping, interface trap generation, and C-V hysteresis were significantly reduced (< 50%) in HfO2/SiO2 stacks with engineered fluorine profile. Fluorine is suggested to effectively passivate charge trapping sites located at the HfO2/SiO2 interface and interface traps at the SiO2/Si interface by forming strong Hf-F and Si-F bonds.

Seo, Kang-Ill

102

Tailoring dielectric relaxation in ultra-thin high-dielectric constant nanolaminates for nanoelectronics  

NASA Astrophysics Data System (ADS)

The work reported here demonstrates the feasibility of controlling the dielectric properties--high dielectric constant (k) and substantially extended relaxation frequency--of thin film nanolaminates (NLs) consisting of alternating TiOx and Al2O3 sublayers with various sublayer thicknesses grown by atomic layer deposition. For 150 nm thick TiOx/Al2O3 NLs with sub-nanometer thick sublayers, few Angstrom change in sublayer thickness dramatically increases relaxation cut-off frequency by more than 3 orders of magnitude with high dielectric constant (k > 800). This unusual phenomenon is discussed in the framework of two-phase Maxwell-Wagner relaxation.

Lee, Geunhee; Lai, Bo-Kuai; Phatak, Charudatta; Katiyar, Ram S.; Auciello, Orlando

2013-04-01

103

Competitive Si and La effect in HfO2 phase stabilization in multi-layer (La2O3)0.08(HfO2) films  

NASA Astrophysics Data System (ADS)

The effect of Si diffusion in HfO2 and the presence of La on phase transformation were investigated. Tetragonal HfO2 structures exhibited high permittivity, and the addition of exotic atoms to HfO2 facilitated tetragonal phase transformation. In multi-layer (La2O3)0.08(HfO2) films, the top HfO2 layer was transformed into a perfect tetragonal structure, and the bottom HfO2 layer near the interfacial layer was of a cubic structure, after annealing at 800 °C. The permittivity reached 50-60. Si diffusion into the HfO2 film stabilized the tetragonal structure, and La incorporation into HfO2 facilitated the transition of the cubic structure.

Cao, Duo; Cheng, Xinhong; Yu, Yuehui; Li, Xiaolong; Liu, Chunze; Shen, Dashen; Mändl, Stephan

2013-08-01

104

Determination of annealing of temperature HfO2/Si metal-oxide-semiconductor devices  

NASA Astrophysics Data System (ADS)

Thermal behavior of thin high-k dielectric films (˜ 8.4 nm) of HfO2, deposited by reactive rf-sputtering technique on n-type Si (100) wafer, is studied by thermogravimetry (TG) and Differential Scanning Calorimetry (DSC) techniques. DSC results reflect partial crystallization of the film which starts at 250 °C and another transformation begins beyond 670 °C. The high-frequency (HF) capacitance - voltage (C-V) characteristics, measured for all the devices, annealed at different temperatures also corroborate the above observation.

Biswas, Debaleen; Faruque, Sk. Abdul Kader Md.; Chakraborty, Supratic

2014-04-01

105

Dopant compensation in HfO2 and other high K oxides  

NASA Astrophysics Data System (ADS)

The theory of doping limits in semiconductors and insulators is applied to the case of wide gap oxides, crystalline, or amorphous, and used to explain that impurities do not in general give rise to gap states or a doping response. Instead, the system tends to form defect complexes or undergo symmetry-lowering reconstructions to expel gap states out of the band gap. The model is applied to impurities, such as trivalent metals, carbon, N, P, and B, in HfO2, the main gate dielectric used in field effect transistors.

Li, H.; Guo, Y.; Robertson, J.

2014-05-01

106

Characteristics of HfO2 and SiO2 on p-type silicon wafers using terahertz spectroscopy  

NASA Astrophysics Data System (ADS)

The effect of high-? dielectric HfO2 films on 200 mm diameter p-type silicon substrates was investigated and compared with conventional dielectric material, SiO2. We employed all-optical characterization methods using terahertz (THz) time-domain spectroscopy and visible cw pump/THz probe spectroscopy. Measurements were performed on two sets of samples, each set containing both HfO2 and SiO2 coated wafers with varying thickness of oxide layer. One set had a protective coating of either photoresist or Si3N4 deposition above the oxide layer which in turn was on a heavily doped p+ layer on p-type silicon. The samples exhibited similar linear transmission in the THz frequency range studied. However, when using an Ar+-ion laser as an optical pump source, differential measurements (with and without the pump source) showed that the transmission was far smaller for the high-? dielectric HfO2 films than its conventional dielectric SiO2 counterparts, indicating the presence of large photo-generated carrier density in the p-type substrate.

Altan, H.; Sengupta, A.; Pham, D.; Grebel, H.; Federici, J. F.

2007-05-01

107

Reduction of thermal damage in ultrathin gate oxides after intrinsic dielectric breakdown  

NASA Astrophysics Data System (ADS)

We have compared the thermal damage in ultrathin gate SiO2 layers of 5.6 and 3 nm thickness after intrinsic dielectric breakdown due to constant voltage Fowler-Nordheim stress. The power dissipated through the metal-oxide-semiconductor capacitor during the breakdown transient, measured with high time resolution, strongly decreases with oxide thickness. This is reflected in a noticeable reduction of the thermal damage found in the structure after breakdown. The effect can be explained as the consequence of the lower amount of defects present in the oxide at the breakdown instant and of the occurrence of a softer breakdown in the initial spot. The present data allow us to estimate the power threshold at the boundary between soft and hard breakdown, and they are compared to numerical simulations of heat flow.

Lombardo, S.; La Magna, A.; Crupi, I.; Gerardi, C.; Crupi, F.

2001-09-01

108

Ultrathin aluminum oxide gate dielectric on N-type 4H-SiC prepared by low thermal budget nitric acid oxidation  

Microsoft Academic Search

MOS capacitors with an ultrathin aluminum oxide (Al2O3) gate dielectric were fabricated on n-type 4H-SiC. Al2O3 was prepared by room-temperature nitric acid (HNO3) oxidation of ultrathin Al film followed by furnace annealing. The effective dielectric constant of k?9.4 and equivalent oxide thickness of 26 Å are produced, and the interfacial layer and carbon clusters are not observed in this paper.

Szu-Wei Huang; Jenn-Gwo Hwu

2004-01-01

109

Photoemission studies of the initial interface formation of ultrathin MgO dielectric layers on the Si(111) surface  

Microsoft Academic Search

This study investigates the interface formation between a magnesium oxide dielectric overlayer and an ultrathin SiO2 layer (?0.3 nm) grown on the atomically clean p-type Si(111) surface in ultra high vacuum. Both soft X-ray synchrotron radiation based photoemission and conventional X-ray photoelectron spectroscopy have been used to characterise the evolution of the interface and monitor the change in the interfacial oxide

Barry Brennan; Stephen McDonnell; Greg Hughes

2010-01-01

110

Characterization of local dielectric breakdown in ultrathin SiO2 films using scanning tunneling microscopy and spectroscopy  

Microsoft Academic Search

Local dielectric breakdown of ultrathin SiO2 films grown on silicon substrates has been investigated by using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). We found that STM observation can reveal individual quasibreakdown spots created by hot-electron injection into the oxide, as well as features of the topography such as atomic steps on the oxide surface. STS was used

Heiji Watanabe; Toshio Baba; Masakazu Ichikawa

1999-01-01

111

Atomic layer deposition of an Al2O3 dielectric on ultrathin graphite by using electron beam irradiation  

NASA Astrophysics Data System (ADS)

Atomic layer deposition of an Al2O3 dielectric on ultrathin graphite is studied in order to investigate the integration of a high k dielectric with graphite-based substrates. Electron beam irradiation on the graphite surface is followed by a standard atomic layer deposition of Al2O3. Improvement of the Al2O3 layer deposition morphology was observed when using this radiation exposure on graphite. This result may be attributed to the amorphous change of the graphite layers during electron beam irradiation.

Ran, Jiang; Lingguo, Meng; Xijian, Zhang; Jung, Hyung-Suk; Hwang, Cheol Seong

2012-09-01

112

Synthesis of freestanding HfO2 nanostructures  

PubMed Central

Two new methods for synthesizing nanostructured HfO2 have been developed. The first method entails exposing HfTe2 powders to air. This simple process resulted in the formation of nanometer scale crystallites of HfO2. The second method involved a two-step heating process by which macroscopic, freestanding nanosheets of HfO2 were formed as a byproduct during the synthesis of HfTe2. These highly two-dimensional sheets had side lengths measuring up to several millimeters and were stable enough to be manipulated with tweezers and other instruments. The thickness of the sheets ranged from a few to a few hundred nanometers. The thinnest sheets appeared transparent when viewed in a scanning electron microscope. It was found that the presence of Mn enhanced the formation of HfO2 by exposure to ambient conditions and was necessary for the formation of the large scale nanosheets. These results present new routes to create freestanding nanostructured hafnium dioxide. PACS: 81.07.-b, 61.46.Hk, 68.37.Hk.

2011-01-01

113

Electrical Properties and Defect Structure of HFO2.  

National Technical Information Service (NTIS)

The defect structure of high-purity, polycrystalline HfO2 was investigated by measuring the oxygen partial pressure dependence of the electrical conductivity and the sample weight. From 1000 to 1500C and above oxygen partial pressures of 0.000001, the con...

N. M. Tallan W. C. Tripp R. W. Vest

1967-01-01

114

Extrinsic interface formation of HfO2 and Al2O3/GeOx gate stacks on Ge (100) substrates  

NASA Astrophysics Data System (ADS)

The extrinsic interfaces present at the HfO2/GeOx/Ge and Al2O3/GeOx/Ge gate stacks are investigated. The effective trapped charge density, estimated from hysteresis in capacitance-voltage characteristics, is higher for HfO2 than for Al2O3, implying qualitatively different charge trapping sources in each dielectric. Spectroscopic ellipsometry and medium energy ion scattering measurements reveal that HfO2 deposition induces the formation of a thicker germanate (intermixed) layer at the HfO2/GeOx interface, where nonstoichiometric Ge-rich GeOx having significantly low bandgap (~1.8 eV) is present. In contrast, Al2O3 deposition leads to an abrupt and thinner O-rich GeOx interfacial layer without Ge-rich GeOx phase. The proposed band alignment indicates that Ge-rich GeOx layer at HfO2/GeOx arises a significant band potential well trapping, while O-rich GeOx layer in Al2O3/GeOx is responsible for a relatively lower charge trapping at band potential well. The combined results strongly suggest that the control of the GeOx interface layers is crucial to reduce the high charge trapping at high-?/GeOx/Ge gate stacks.

Seo, H.; Bellenger, F.; Chung, K. B.; Houssa, M.; Meuris, M.; Heyns, M.; Lucovsky, G.

2009-08-01

115

Dielectric polarization and refractive indices of ultrathin barium titanate films on strontium titanate single crystals.  

PubMed

The electrical and optical properties of ultrathin films of tetragonal barium titanate (BaTiO(3)) on strontium titanate (SrTiO(3)) single-crystal substrates are theoretically investigated using a microscopic quantum mechanical model based on the orbital approximation in correlation with the dipole-dipole interaction. First-, second-, and third-order electronic polarizabilities had to be considered in this calculation in order to obtain accurate results for both the dielectric spontaneous polarization and the refractive indices of the BaTiO(3) overlayer. The spontaneous polarization is drastically reduced in the film as its thickness decreases. However, an electronic polarization appears within the SrTiO(3) substrate in the neighbourhood of the interface. This polarization, which vanishes far away from the interface into the SrTiO(3) bulk, is induced by the polarization of the BaTiO(3) film. Furthermore, we find the refractive index for both the BaTiO(3) film and the SrTiO(3) substrate to be deeply reduced for light polarized perpendicular to the surface. PMID:21690676

Chaib, H; Eng, L M; Otto, T

2005-01-12

116

Epitaxial growth and electrical properties of ultrathin La2Hf2O7 high-k gate dielectric films  

NASA Astrophysics Data System (ADS)

Ultrathin La2Hf2O7 (LHO) high-k gate dielectric films (˜3.4 nm) have been epitaxially grown on Si (0 0 1) substrates through a pulsed laser deposition system. The epitaxial growth characteristics, composition, interface with Si, optical band gap, and electrical properties of the ultrathin LHO films have been investigated by in situ reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS) and transmittance spectroscopy, as well as semiconductor characterization analysis. Results show that ultrathin LHO film grown at 800 °C shows a good crystallinity and no obvious interfacial layer forms. La is deficient and oxygen is slightly excessive in LHO film. The epitaxial LHO film has a band gap of ˜5.7 eV. The gate leakage current density Jg of the ultrathin epitaxial LHO film follows the space-charge limited conduction mechanism and Jg is ˜0.3 A/cm2 at a gate voltage of 1 V. Additionally, a suitable permittivity ˜ 16.7, a small hysteresis ˜ 30 mV and a low capacitance equivalent thickness ˜ 0.79 nm have been obtained.

Xiong, Yu-Hua; Tu, Hai-Ling; Du, Jun; Wei, Feng; Zhang, Xin-Qiang; Yang, Meng-Meng; Zhao, Hong-Bin; Chen, Da-Peng; Wang, Wen-Wu

2013-10-01

117

Synthesis and microstructure of Gd 2O 3-doped HfO 2 ceramics  

Microsoft Academic Search

The effect of Gd2O3-doping on the crystal structure, surface morphology and chemical composition of the Gd2O3–HfO2 system is reported. Gd2O3–HfO2 ceramics with variable composition were prepared by varying the Gd2O3 composition in the range of 0–38mol% balanced HfO2. X-ray diffraction (XRD) analysis indicates that the Gd2O3 concentration influences the crystal structure of the Gd2O3–HfO2 ceramics. Pure HfO2 and Gd2O3 crystallize

C. K. Roy; M. Noor-A-Alam; A. R. Choudhuri; C. V. Ramana

118

Topology dependent electronic and dielectric properties of free standing alloyed ultrathin nanowires of noble metals  

NASA Astrophysics Data System (ADS)

Structural, electronic and dielectric properties of free standing ultrathin alloyed nanowires of noble metals (AgAu, AgCu, AgPt, AuCu, AuPt and CuPt) in various topologies (linear, ladder and double zigzag) have been studied by using ab initio density functional theory. Among the different topologies of alloyed ultrathin nanowires of noble metals, double zigzag (DZZ) topology has been found to be most stable and the linear topology the least stable. Also the binding energy of alloyed nanowires of AgAu and AuCu for all the studied topologies is found to be larger than the average binding energy of the corresponding pristine nanowires, indicating a strong alloying effect for these topologies. Among electronic properties, the alloyed nanowires of different topologies containing Pt (AgPt, AuPt and AuCu) are found to be ferromagnetic in nature, a result of d charge depletion in Ag, Au and Cu sites and d charge gain at Pt sites. On the other hand, all the topologies (except ladder topology) of alloyed nanowires viz. AgAu, AgCu and AuCu are found to be semiconducting in nature. The optical properties of the studied alloyed nanowires have been found to be different from their corresponding pristine nanowires due to change in the band structure on alloying. The linear topology of AgAu, AgCu and AuCu and DZZ topologies (DZZ1, DZZ2 and DZZ3) of Ag, Au, Cu, AgAu, AgCu and AuCu are semiconducting in nature with band gap lying in the infrared region, causing absorption of photons from a visible spectrum leading to blackish appearance. Whereas, remaining topologies are found to be metallic in nature, with plasmon frequency lying in the energy range of 0.35 eV to 1.62 eV, which is in the infrared region and hence these nanowires shall appear to be transparent to the visible region.

Kumar, Arun; Kumar, Ashok; Ahluwalia, P. K.

2014-08-01

119

Solid-State Densification of Spun-Cast Self-Assembled Monolayers for Use in Ultra-Thin Hybrid Dielectrics  

PubMed Central

Ultra-thin self-assembled monolayer (SAM)-oxide hybrid dielectrics have gained significant interest for their application in low-voltage organic thin film transistors (OTFTs). A [8-(11-phenoxy-undecyloxy)-octyl]phosphonic acid (PhO-19-PA) SAM on ultrathin AlOx (2.5 nm) has been developed to significantly enhance the dielectric performance of inorganic oxides through reduction of leakage current while maintaining similar capacitance to the underlying oxide structure. Rapid processing of this SAM in ambient conditions is achieved by spin coating, however, as-cast monolayer density is not sufficient for dielectric applications. Thermal annealing of a bulk spun-cast PhO-19-PA molecular film is explored as a mechanism for SAM densification. SAM density, or surface coverage, and order are examined as a function of annealing temperature. These SAM characteristics are probed through atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and near edge X-ray absorption fine structure spectroscopy (NEXAFS). It is found that at temperatures sufficient to melt the as-cast bulk molecular film, SAM densification is achieved; leading to a rapid processing technique for high performance SAM-oxide hybrid dielectric systems utilizing a single wet processing step. To demonstrate low-voltage devices based on this hybrid dielectric (with leakage current density of 7.7×10?8 A cm?2 and capacitance density of 0.62 µF cm?2 at 3 V), pentacene thin-film transistors (OTFTs) are fabricated and yield sub 2 V operation and charge carrier mobilites of up to 1.1 cm2 V?1 s?1.

Hutchins, Daniel O.; Acton, Orb; Weidner, Tobias; Cernetic, Nathan; Baio, Joe E.; Castner, David G.; Ma, Hong; Jen, Alex K.-Y.

2013-01-01

120

Quantitatively enhanced reliability and uniformity of high-? dielectrics on graphene enabled by self-assembled seeding layers.  

PubMed

The full potential of graphene in integrated circuits can only be realized with a reliable ultrathin high-? top-gate dielectric. Here, we report the first statistical analysis of the breakdown characteristics of dielectrics on graphene, which allows the simultaneous optimization of gate capacitance and the key parameters that describe large-area uniformity and dielectric strength. In particular, vertically heterogeneous and laterally homogeneous Al2O3 and HfO2 stacks grown via atomic-layer deposition and seeded by a molecularly thin perylene-3,4,9,10-tetracarboxylic dianhydride organic monolayer exhibit high uniformities (Weibull shape parameter ? > 25) and large breakdown strengths (Weibull scale parameter, E(BD) > 7 MV/cm) that are comparable to control dielectrics grown on Si substrates. PMID:23387502

Sangwan, Vinod K; Jariwala, Deep; Filippone, Stephen A; Karmel, Hunter J; Johns, James E; Alaboson, Justice M P; Marks, Tobin J; Lauhon, Lincoln J; Hersam, Mark C

2013-03-13

121

First-principles study of dielectric properties of bulk NaCl and ultrathin NaCl films under a finite external electric field  

Microsoft Academic Search

We present a first-principles study of the dielectric properties of a NaCl crystal and ultrathin NaCl films under a finite external electric field. Our results show that the high-frequency dielectric constant of the films is less affected by the finite-size effect from crystal surfaces and is close to that of the crystal, whereas the static one is sensitive to the

Tomoya Ono; Kikuji Hirose

2005-01-01

122

Ultrathin nitride\\/oxide (N\\/O) gate dielectrics for p+-polysilicon gated PMOSFETs prepared by a combined remote plasma enhanced CVD\\/thermal oxidation process  

Microsoft Academic Search

Ultrathin nitride-oxide (N\\/O~1.5\\/2.6 nm) dual layer gate dielectrics have been incorporated into PMOSFETs with boron-implanted polysilicon gates. Boron penetration is effectively suppressed by the top plasma-deposited nitride layer leading to improved short channel performance as compared to PMOSFETs with oxide dielectrics. In addition, improved interface characteristics and hot carrier degradation immunity are also demonstrated for the devices with the N\\/O

Yider Wu; Gerald Lucovsky

1998-01-01

123

Critical thickness for extrinsic contributions to the dielectric and piezoelectric response in lead zirconate titanate ultrathin films  

NASA Astrophysics Data System (ADS)

Highly (100)-textured Pb(Zr0.53Ti0.47)O3 films (Lotgering factors >=90%) with thicknesses ranging from 20 to 260 nm were grown on platinized Si substrates using sol-gel deposition. Ferroelectric hysteresis, low field dielectric permittivity, and nonlinear dielectric response as well as converse longitudinal piezoelectric response (d33,f) of the ultrathin films were studied at 1 kHz. The measurements revealed the existence of a critical film thickness, ~50 nm, below which the extrinsic contributions to the dielectric response are almost completely suppressed. Piezoelectric response of the films also showed a significant (~50%) drop at the same critical thickness. Due to the columnar microstructure of these films the critical dimension of the ferroelectric is represented by the thickness rather than the lateral grain size, where the latter is invariant across the samples. The critical thickness led also to a deviation of the thickness dependence of the dielectric permittivity from the in-series capacitors model frequently representing ``interfacial dead layers.'' The critical size is attributed to significant reduction in domain wall population and/or mobility in films thinner than ~50 nm.

Bastani, Yaser; Schmitz-Kempen, Thorsten; Roelofs, Andreas; Bassiri-Gharb, Nazanin

2011-01-01

124

Effects of ozone post deposition treatment on interfacial and electrical characteristics of atomic-layer-deposited Al2O3 and HfO2 films on GaSb substrates  

NASA Astrophysics Data System (ADS)

Atomic-layer-deposited Al2O3 and HfO2 films on GaSb substrates were treated by in-situ ozone post deposition treatment (PDT). The effects of ozone PDT on the interfacial and electrical properties of Al2O3 and HfO2 gate dielectric films on GaSb substrates were investigated carefully. It is found that the dielectric quality and the interfacial properties of the Al2O3 and HfO2 films are improved by ozone PDT. After in-situ ozone PDT for 5 min, the Al2O3 and HfO2 films on GaSb substrates exhibit improved electrical and interfacial properties, such as reduced frequency dispersion, gate leakage current, border traps and interface traps. Interface trap density is reduced by ˜24% for the Al2O3/GaSb stacks and ˜27% for the HfO2/GaSb stacks. In-situ ozone PDT is proved to be a promising technique in improving the quality of high-k gate stacks on GaSb substrates.

Zhao, Lianfeng; Tan, Zhen; Wang, Jing; Xu, Jun

2014-01-01

125

Electron beam induced local crystallization of HfO2 nanopores for biosensing applications.  

PubMed

We report the development of single, locally crystallized nanopores in HfO2 membranes for biosensing applications. HfO2 is chosen for its isoelectric point of 7.0, mechanical and chemical stability in solution, and for its potential as a high-k material for nanopore ionic field effect transistor applications. The HfO2 membrane is deposited on a graphene layer suspended over a 300 nm FIB hole, where graphene is used as the mechanical support. Exposure of the membrane to a focused electron beam causes crystallization in the vicinity of the nanopore during pore formation. We investigate the effects of crystallization on the electrical and surface properties of HfO2 films. Our surface analysis of HfO2 reveals improved hydrophilicity of crystallized HfO2, a notable advantage over the hydrophobicity of as-deposited HfO2. We also demonstrate detection of dsDNA translocation through HfO2 nanopores under various applied bias levels. In addition, our device architecture also presents a promising first step toward the realization of high-k HfO2 nanopore transistors. PMID:23945603

Shim, Jiwook; Rivera, Jose A; Bashir, Rashid

2013-11-21

126

Germanium diffusion during HfO2 growth on Ge by molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

The authors study the Ge diffusion during HfO2 growth by molecular beam epitaxy on differently in situ prepared germanium substrates and at different growth temperatures. While HfO2 layers grown directly on Ge do not show any germanium contamination, oxygen rich interfacial layers such as GeOx or GeOxNy partly dissolve into the HfO2 layer, giving rise to high Ge contamination (from 1% to 10%). The use of nitridated interfacial layers does not prevent Ge diffusion into the HfO2 during the growth process because of the high oxygen content present in the nitridated germanium layer.

Ferrari, S.; Spiga, S.; Wiemer, C.; Fanciulli, M.; Dimoulas, A.

2006-09-01

127

Optimization of pH sensing using silicon nanowire field effect transistors with HfO2 as the sensing surface  

Microsoft Academic Search

Silicon nanowire field effect transistor sensors with SiO2\\/HfO2 as the gate dielectric sensing surface are fabricated using a top down approach. These sensors are optimized for pH sensing with two key characteristics. First, the pH sensitivity is shown to be independent of buffer concentration. Second, the observed pH sensitivity is enhanced and is equal to the Nernst maximum sensitivity limit

Sufi Zafar; Christopher D’Emic; Ali Afzali; Benjamin Fletcher; Y. Zhu; Tak Ning

2011-01-01

128

Impact of the crystal structure of HfO2 on the transport properties of model HfO2/Si/HfO2 silicon-on-insulator field-effect transistors: A combined DFT-scattering theory approach  

NASA Astrophysics Data System (ADS)

Motivated by the polycrystalline structure of the high permittivity dielectric HfO2 in contact with Si, we report calculations of carrier transport in nanometer-thin atomistic silicon-on-insulator field-effect transistor models. To qualitatively understand the impact of different crystalline phases of the dielectric on the transport characteristics of the channel, we have investigated two polymorphs of HfO2 interfacing with Si, namely, the well-known tetragonal (t-HfO2) and the theoretically proposed anatase (a-HfO2) phases. For the transport calculations we have employed tetragonal- (t-HfO2/Si/t-HfO2) and anatase-based (a-HfO2/Si/a-HfO2) NSOI films. Our calculations reveal that transport is more efficient for the anatase polymorph since its good lattice match to Si does not create interface states in the Si band gap. The tetragonal polymorph creates scattering states in the Si band valence-band edge through the presence of stretched Si-Si bonds at the interface, resulting in degraded transport characteristics. Our study suggests that different bonding arrangements along the channel length create regions of increased carrier scattering even in the absence of other scattering processes such as phonons, trapped charges, or interface roughness.

Giorgi, G.; Fonseca, L. R. C.; Korkin, A.; Yamashita, K.

2009-06-01

129

Energy band alignment of HfO2 on Ge  

NASA Astrophysics Data System (ADS)

The band alignment of hafnium oxide films grown on Ge (100) by atomic layer deposition has been investigated by x-ray photoelectron spectroscopy (XPS) and internal photoemission (IPE) spectroscopy. HfO2 films have been grown using HfCl4 as hafnium precursor while O3 or H2O have been used as oxygen precursors. The valence-band offset (VBO) values, determined by XPS, are 3.0+/-0.1 eV and 3.1+/-0.1 eV for the samples grown using O3 and H2O, respectively. A conduction-band offset (CBO) value of 2.0+/-0.1 eV has been obtained by IPE for all the samples. Considering a band gap of 5.6+/-0.1 eV, as obtained by photoconductivity measurements, XPS and IPE results have been found to be in excellent agreement. The CBO and VBO values are the same in all the samples within the experimental error. The presence of a thick GeOx interfacial layer in the samples grown using O3 is not affecting the band alignment of the HfO2/Ge heterojunction.

Perego, M.; Seguini, G.; Fanciulli, M.

2006-11-01

130

Vacuum ultraviolet thin films. I - Optical constants of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 thin films. II - Vacuum ultraviolet all-dielectric narrowband filters  

NASA Technical Reports Server (NTRS)

An iteration process matching calculated and measured reflectance and transmittance values in the 120-230 nm VUV region is presently used to ascertain the optical constants of bulk MgF2, as well as films of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 deposited on MgF2 substrates. In the second part of this work, a design concept is demonstrated for two filters, employing rapidly changing extinction coefficients, centered at 135 nm for BaF2 and 141 nm for SiO2. These filters are shown to yield excellent narrowband spectral performance in combination with narrowband reflection filters.

Zukic, Muamer; Torr, Douglas G.; Spann, James F.; Torr, Marsha R.

1990-01-01

131

Ultra-thin film and interface analysis of high-k dielectric materials employing Time-Of-Flight Medium Energy Ion Scattering (TOF-MEIS)  

NASA Astrophysics Data System (ADS)

We explore the potential of Time-Of-Flight Medium Energy Ion Scattering (TOF-MEIS) for thin film analysis and analyze possible difficulties in evaluation of experimental spectra. As a model system high-k material stacks made from ultra-thin films of HfO2 grown on a p-type Si (1 0 0) substrate with a 0.5 nm SiO2 interface layer have been investigated. By comparison of experimental spectra and computer simulations TOF-MEIS was employed to establish a depth profile of the films and thus obtaining information on stoichiometry and film quality. Nominal film thicknesses were in the range from 1.8 to 12.2 nm. A comparison of the results with those from other MEIS approaches is made. Issues regarding different combinations of composition and stopping power as well as the influence of channeling are discussed. As a supporting method Rutherford-Backscattering spectrometry (RBS) was employed to obtain the areal density of Hf atoms in the films.

Primetzhofer, D.; Dentoni Litta, E.; Hallén, A.; Linnarsson, M. K.; Possnert, G.

2014-08-01

132

HfO2 based memory devices with rectifying capabilities  

NASA Astrophysics Data System (ADS)

We report on the fabrication and characterization of metal/insulator/metal capacitor like devices, with both rectifying and hysteretic features. Devices are formed by two junctions, Ti/HfO2 and Co/HfO2. Each junction exhibits highly repetitive hysteretic I-V curves with a sharp transition from a high to a low resistance state (3-4 orders of magnitude jump). The opposite transition (from low to high) is induced by polarity reversal. The rectifying non-crossing characteristics of the I-V branches denote their potential use as a multifunctional device, acting as a built-in rectifier and memory cell in a single device. Based on the phenomenological model description by Zazpe et al. [Appl. Phys. Lett. 103, 073114 (2013)], we propose a circuital equivalent representation supported on switchable rectifying junctions. By exploring different electrode connections, we disentangle the role of the bulk transport in HfO2 devices.

Quinteros, C.; Zazpe, R.; Marlasca, F. G.; Golmar, F.; Casanova, F.; Stoliar, P.; Hueso, L.; Levy, P.

2014-01-01

133

Improved performance of non-volatile memory with Au-Al2O3 core-shell nanocrystals embedded in HfO2 matrix  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate a charge trapping memory with Au-Al2O3 core-shell nanocrystals (NCs) embedded in HfO2 high-k dielectric. Transmission electron microscopy images clearly show the Au NCs surrounded by Al2O3 shells in the HfO2 matrix. Electrical measurements show a considerable memory window (3.6 V at +/-8 V), low program/erase operation voltages, and good endurance. Particularly, data retention is improved both at room temperature and high temperature compared to the NC structure without shell. An energy band model is given for the improved retention characteristic. This Au-Al2O3 core-shell NCs memory device has a strong potential for future high-performance nonvolatile memory application.

Xu, Zhongguang; Zhu, Chenxin; Huo, Zongliang; Cui, Yanxiang; Wang, Yumei; Li, Fanghua; Liu, Ming

2012-05-01

134

Interfacial characteristics of HfO2 films grown on strained Si0.7Ge0.3 by atomic-layer deposition  

NASA Astrophysics Data System (ADS)

The interfacial characteristics of gate stack structure of HfO2 dielectrics on strained Si0.7Ge0.3 deposited by atomic-layer deposition were investigated. An interfacial layer including GeOx layers was grown on a SiGe substrate, and the thickness of the GeOx layer at the interfacial layer was decreased after the annealing treatment, while SiO2 layer was increased. The ~50-Å-thick HfO2 film with an amorphous structure was converted into a polycrystalline structure after rapid annealing at temperature of over 700 °C for 5 min. The interfacial silicate layer was effectively suppressed by GeOx formation, while the silicate layer was formed after the annealing treatment. GeOx formation in an as-grown film resulted in a decrease in the accumulation capacitance and an increase in the oxide trap charge.

Cho, M.-H.; Chang, H. S.; Moon, D. W.; Kang, S. K.; Min, B. K.; Ko, D.-H.; Kim, H. S.; McIntyre, Paul C.; Lee, J. H.; Ku, J. H.; Lee, N. I.

2004-02-01

135

Schottky barrier height reduction for metal/n-InP by inserting ultra-thin atomic layer deposited high-k dielectrics  

NASA Astrophysics Data System (ADS)

Fermi level pinning at metal/n-InP interface and effective Schottky barrier height (?B,eff) were optimized by inserting ultrathin dielectrics in this work. Comparing the inserted monolayer and bilayer high-k dielectrics, we demonstrated that the introduction of bilayer dielectrics can further reduce ?B,eff (from 0.49 eV to 0.22 eV) than the monolayer dielectric (from 0.49 eV to 0.32 eV) even though the overall dielectric thickness was thicker. The additional dipole formed at high-k/high-k interfaces could be used to expound the mechanism. This work proposed an effective solution to reduce resistance contacts for InP based transistors and Schottky barrier transistors.

Zheng, Shan; Yang, Wen; Sun, Qing-Qing; Chen, Lin; Zhou, Peng; Wang, Peng-Fei; Wei Zhang, David; Xiao, Fei

2013-12-01

136

Acoustic spectroscopy and electrical characterization of Si/NAOS-SiO2/HfO2 structures  

NASA Astrophysics Data System (ADS)

The MOS structure prepared on n-type Si substrate with SiO2/HfO2 gate dielectric layers was formed by 5 nm HfO2 oxide deposited by atomic layer deposition on 0.6 nm SiO2 oxide film prepared with nitric acid oxidation of Si (NAOS) in ˜100% HNO3 vapor. The set of this MOS structure was annealed in N2 atmosphere at 200, 300 and 400 °C for 10 min to stabilize the structure, to decrease the interface states density and leakage current density. The both acoustic deep level transient spectroscopy (A-DLTS) and acoustoelectric response signal versus gate voltage dependence (Uac-Ug characteristics) were used to characterize the interface states and the role of annealing treatment, except ordinary electrical investigation represented by current-voltage and capacitance-voltage measurements. The main interface deep centers with activation energies ˜0.30 eV typical for dangling-bond type defects were observed as well as a particular influence of annealing treatment on the interface states. The obtained results are analyzed and discussed.

Bury, Peter; Matsumoto, Taketoshi; Bellan, Ivan; Janek, Marián; Kobayashi, Hikaru

2013-03-01

137

Properties of Ultrathin Al2O3-TiO2 Nanolaminate Films for Gate Dielectric Applications Deposited by Plasma-Assisted Atomic Layer Deposition  

NASA Astrophysics Data System (ADS)

High permittivity dielectrics such as Al2O3, HfO2, Ta2O5, TiO2, etc., are an essential component of aggressively-scaled III-V and graphene field effect transistors (FETs) where insulators are necessary to reduce gate leakage current while maintaining high gate capacitance and charge control of the channel. Atomic layer deposition (ALD) has the capability to deposit hybrid films, or nanolaminates, of two or more dielectrics that have unique properties. Thin [Al2O3+TiO2] nanolaminates with varying TiO2 and Al2O3 content were deposited on n-Si substrates at ˜225-300 C using ALD. A nanolaminate is composed of bilayers, defined as the sum of (x)Al2O3 and (y)TiO2, where x, and y indicate the number of times a component monolayer is repeated. While the overall thickness of the dielectric was held at ˜ 17-20 nm, the relative ratio of Al2O3 to TiO2 in the bilayer stack was varied to evaluate changes in the material properties and electrical performance of the oxides. C-V and I-V measurements on various [(x)TiO2+(y)Al2O3] MOS capacitors were taken. The high-TiO2-content films show limited evidence of oxide charge trapping and relatively large dielectric constants (?˜15), whereas the high-Al2O3-content films offer a larger optical bandgap and improved suppression of leakage current. We will discuss the properties of very thin nanolaminates and their possible use as gate oxides. Morphological, electrical, and XPS composition assessments will be presented.

Garces, Nelson; Meyer, David; Nepal, Neeraj; Wheeler, Virginia; Eddy, Charles

2012-02-01

138

DC and RF characteristics of advanced MIM capacitors for MMIC's using ultra-thin remote-PECVD Si3N4 dielectric layers  

Microsoft Academic Search

We have fabricated advanced metal-insulator-metal (MIM) capacitors with ultra-thin (200 Å) remote-PECVD Si3N4 dielectric layers having excellent electrical properties. The breakdown field strength of MIM capacitors with 200-Å-thick Si3N 4 was larger than 3.5 MV\\/cm, which indicates the excellent quality of the deposited Si3N4 film. The main capacitance per unit area extracted by radio frequency (RF) measurements was as high

Jae-Hak Lee; Dae-Hyun Kim; Yong-Soon Park; Myoung-Kyu Sohn; Kwang-Seok Seo

1999-01-01

139

Interface and plasma damage analysis of PEALD TaCN deposited on HfO2 for advanced CMOS studied by angle resolved XPS and C-V  

NASA Astrophysics Data System (ADS)

Plasma enhanced atomic layer deposition (PEALD) TaCN deposited on HfO2 was studied by X-ray photoelectron spectroscopy (XPS) to understand the reactions taking place at the interface and connect them with C-V electrical characteristics of MOS devices. Moreover, angular resolved XPS (AR-XPS) was used for composition depth profiling of TaCN/HfO2/SiO2/Si stacks. Clear oxidation of the metal electrode through Tasbnd O bonding formation and migration of N in the dielectric with Hfsbnd N are shown. These modifications of chemical bonding give an insight on the electrical results. Low equivalent oxide thicknesses (EOT), as low as 0.89 nm and current leakage improvement by more than 5 decades, are observed for deposition with low plasma power and can be related to HfN content in HfO2 layer. The increase of plasma power used for TaCN deposition results in densification of the layer and promotes the creation of TaC in TaCN material. However H2 plasma has an impact on HfO2 with a reduction and scattering of the measured current leak gain. TaCN/HfO2 interface is also impacted with further creation of TaOx, leading to an increase of EOT when plasma power is increased. Based on these findings, reaction mechanisms with the corresponding Gibbs free energy are proposed.

Piallat, Fabien; Beugin, Virginie; Gassilloud, Remy; Dussault, Laurent; Pelissier, Bernard; Leroux, Charles; Caubet, Pierre; Vallée, Christophe

2014-06-01

140

Materials and electrical characterization of molecular beam deposited CeO2 and CeO2/HfO2 bilayers on germanium  

NASA Astrophysics Data System (ADS)

Properties of CeO2 and CeO2/HfO2 bilayers grown by molecular beam deposition on in situ prepared, oxide-free Ge(100) surfaces are reported here. Deposition is achieved by a simultaneous flux of electron-beam evaporated metal (Ce or Hf) and of remote plasma generated atomic oxygen. These conditions result in an interfacial layer (IL) between the cubic CeO2 and Ge substrate. Electron energy loss spectroscopy shows that this IL is comprised of Ge and O and a small amount of Ce, and x-ray photoelectron spectroscopy suggests that the Ge is in a mix of 2+ and 3+ oxidation states. A comparison of capacitance, conductance, and leakage data shows a higher quality dielectric for 225 °C deposition than for room temperature. However, CeO2-only deposition results in an unacceptably high leakage current due to the small CeO2 band gap, which is remedied by the use of CeO2/HfO2 bilayers. Using the Nicollian-Goetzberger method, interface trap densities in the mid 1011 eV-1 cm-2 are obtained for CeO2/HfO2 gate stacks on both n- and p-Ge.

Brunco, D. P.; Dimoulas, A.; Boukos, N.; Houssa, M.; Conard, T.; Martens, K.; Zhao, C.; Bellenger, F.; Caymax, M.; Meuris, M.; Heyns, M. M.

2007-07-01

141

High-reflectivity HfO2\\/SiO2 ultraviolet mirrors  

Microsoft Academic Search

High-reflectivity dense multilayer coatings were produced for the ultraviolet spectral region. Thin-film single layers and UV mirrors were deposited by ion plating and plasma ion-assisted deposition high-energetic technologies. Optical characterizations of HfO2 and SiO2 single layers are made. The optical constants obtained for these two materials are presented. HfO2 and SiO2 mirrors with a reflectance of approx99% near 250 nm

Philippe Torchio; Alexandre Gatto; Marco Alvisi; Gerard Albrand; Norbert Kaiser; Claude Amra

2002-01-01

142

Electrode dependence of filament formation in HfO2 resistive-switching memory  

Microsoft Academic Search

This study investigates bipolar and nonpolar resistive-switching of HfO2 with various metal electrodes. Supported by convincing physical and electrical evidence, it is our contention that the composition of conducting filaments in HfO2 strongly depends upon the metal electrodes. Nonpolar resistive-switching with the Ni electrode is attributed to the migration of metal cations and the corresponding electrochemical metallization. Conversely, oxygen-deficient filaments

Kuan-Liang Lin; Tuo-Hung Hou; Jiann Shieh; Jun-Hung Lin; Cheng-Tung Chou; Yao-Jen Lee

2011-01-01

143

Bias-temperature instabilities of polysilicon gate HfO2 MOSFETs  

Microsoft Academic Search

Bias-temperature instabilities (BTI) of HfO2 metal oxide semiconductor field effect transistors (MOSFETs) have been systematically studied for the first time. NMOS positive BTI (PBTI) exhibited a more significant Vt instability than that of PMOS negative BTI (NBTI), and limited the lifetime of HfO2 MOSFETs. Although high-temperature forming gas annealing (HT-FGA) improved the interface quality by passivating the interfacial states with

Katsunori Onishi; Rino Choi; Chang Seok Kang; Hag-Ju Cho; Young Hee Kim; Renee E. Nieh; Jeong Han; Siddharth A. Krishnan; M. S. Akbar; J. C. Lee

2003-01-01

144

Electronic Structure Differences in ZrO2 vs. HfO2  

SciTech Connect

While ZrO2 and HfO2 are, for the most part, quite similar chemically, subtle differences in their electronic structures appear to be responsible for differing MO2/Si (M = Zr, Hf) interface stabilities. In order to shed light on the electronic structure differences between ZrO2 and HfO2, we have conducted joint experimental/theoretical studies. Since electron affinities are a sensitive probe of electronic structure, we have measured them by conducting photoelectron spectroscopic experiments on ZrO2- and HfO2-. The electron affinity of HfO2 was determined to be 2.14? 0.03 eV, while that of ZrO2 was determined to be 1.64 ? 0.03 eV. Concurrently, electronic structure calculations were conducted to determine electron affinities, vibrational frequencies, and geometries of these systems. The calculated electron affinities of HfO2 and ZrO2 were found to be 2.05 and 1.62 eV, respectively. The molecular results confirm earlier predictions from solid phases that HfO2 is more ionic than ZrO2. The excess electron in MO2- occupies an sd-type hybrid orbital localized on the M atom (M=Zr, Hf). The structural parameters of ZrO2 and HfO2 were found to be very similar. The difference in geometries between the neutral and the anion is along the symmetrical stretching and bending modes. Together, these studies unveil significant differences in the electronic structures of ZrO2 and HfO2.

Zheng, Weijun; Bowen Jr., K.H.; Li, Jun; Dabkowska, Iwona; Gutowski, Maciej S.

2005-12-22

145

Microstructure-dependent band structure of HfO 2 thin films  

Microsoft Academic Search

The effects of rapid thermal annealing on band structure of HfO2 have been investigated using combinational characterization techniques including X-ray diffraction, X-ray photoelectron spectroscopy and ultraviolet–visible spectrophotometer. The results show that the band structure of the thin film is strongly affected by crystalline structure. Different microstructures of HfO2 formed after annealing at a series of temperatures up to 1000 °C:

Y. B. Zheng; S. J. Wang; C. H. A. Huan

2006-01-01

146

Etching Properties of HfO2 Thin Films in Cl2\\/BCl3\\/Ar Plasma  

Microsoft Academic Search

In this study, we changed two input parameters (pressure vs. gas mixing ratio, RF power and DC bias voltage) and then monitored the effect on HfO2 etch rate and selectivity with Si3N4 and SiO2. When the pressure was fixed at 5 mTorr, etch rate of HfO2 decreased with increasing Cl2 content from 0 to 30% in BCl3\\/Ar plasma. At the

Dong-Pyo Kim; Gwan-Ha Kim; Jong-Chang Woo; Xue Yang; Doo-Seung Um; Chang-Il Kim

2009-01-01

147

Effect of Gate Electrodes on Structure and Electrical Properties of Sputtered HfO2 Thin Films  

NASA Astrophysics Data System (ADS)

High dielectric hafnium oxide films were grown by magnetron sputtering and post heat treatment in nitrogen atmosphere at 500°C for 30 min using vacuum annealing furnace. The film keeps amorphous at 500°C and has better interface quality as revealed by X-ray diffraction and transmission electron microscopy. The influence of TiN and Pt electrodes on the electrical property of the film was compared. For the annealed films, TiN electrode was presented as the optimal one. For the conduction mechanism of Pt/HfO2/p-Si MOS capacitors under gate electron injection, the dominant conduction mechanism at low electric field is Schottky emission. At high electric field, the conversion of current transport mechanism from Schottky emission to trap-assisted tunneling for the annealed HfO2 film occurs at 0.64 MV/cm.

Dong, Ming; Wang, Hao; Shen, Liangping; Ye, Cong; Wei, Qinxiang

2012-10-01

148

Ultrathin ALD-Al2O3 layers for Ge(001) gate stacks: Local composition evolution and dielectric properties  

NASA Astrophysics Data System (ADS)

Correlations among physical and electrical properties of atomic layer deposited (ALD)-Al2O3 on H2O-prepulsed Ge(100) have been investigated to evaluate Al2O3 as an ultrathin interface passivation layer for higher-k/Al2O3/Ge gate stacks. In situ XPS in the ALD environment provides insights into the local composition evolution during the initial stages of ALD, evidencing (a) an incubation regime that may limit the minimum achievable capacitance equivalent thickness (CET) of these gate stacks, and (b) residual hydroxyl incorporation in the film consistent with the observed dielectric constant ~7.2. Thickness scaling of the CET is consistent with a nearly abrupt interface as measured by synchrotron radiation photoemission spectroscopy (SRPES). SRPES studies also reveal that forming gas anneal provides passivation through monolayer-level formation of stoichiometric GeO2, suggesting a complex chemical interaction involving residual -OH groups in the as-grown ALD-Al2O3. Valence and conduction band offsets of prepulsed ALD-Al2O3 with respect to Ge are calculated to be 3.3 +/- 0.1 and 2.6 +/- 0.3 eV, indicating that these layers offer an effective barrier to hole and electron injection.

Swaminathan, Shankar; Sun, Yun; Pianetta, Piero; McIntyre, Paul C.

2011-11-01

149

Synthesis and characterization of gold nanoparticles coated with ultrathin and chemically inert dielectric shells for SHINERS applications.  

PubMed

We very recently reported a new spectroscopic application for expanding the versatility of surface Raman called "shell-isolated nanoparticle-enhanced Raman spectroscopy" or "SHINERS". The most important and most difficult part of the SHINERS experiment is the effective transfer of the strong electromagnetic field from a gold core through the isolating silica or alumina shell to the probed surface. For this it is essential that the chemically inert dielectric shell be ultrathin (2-5 nm) yet pinhole-free. Herein we describe experimental and theoretical aspects of our SHINERS method in more detail. We provide a protocol for the synthesis and characterization of optimized shell-isolated nanoparticles (SHINs), and we examine the advantages of SHINERS nanoparticles over bare gold nanoparticles. We also present high-quality Raman spectra obtained from gold and platinum single-crystal surfaces in an electrochemical environment by our SHINERS technique. SHINERS is a simple and cost-effective approach that expands the flexibility of surface-enhanced Raman scattering (SERS) for an unprecedented diversity of applications in materials and surface sciences. PMID:21639983

Li, Jian-Feng; Li, Song-Bo; Anema, Jason R; Yang, Zhi-Lin; Huang, Yi-Fan; Ding, Yong; Wu, Yuan-Fei; Zhou, Xiao-Shun; Wu, De-Yin; Ren, Bin; Wang, Zhong-Lin; Tian, Zhong-Qun

2011-06-01

150

Dielectric breakdown of ultrathin aluminum oxide films induced by scanning tunneling microscopy  

Microsoft Academic Search

Dielectric breakdown of 7-Å-thick Al2O3 (111) films grown on Ni3Al(111) under ultrahigh vacuum conditions is induced by increasing the bias voltage on the scanning tunneling microscopy tip under constant current feedback. Breakdown is marked by the precipitous retreat of the tip from the surface, and the formation of an elevated feature in the scanning tunneling microscopy image, typically greater than

N. P. Magtoto; C. Niu; B. M. Ekstrom; S. Addepalli; J. A. Kelber

2000-01-01

151

Influence of ZrO 2 in HfO 2 on reflectance of HfO 2\\/SiO 2 multilayer at 248 nm prepared by electron-beam evaporation  

Microsoft Academic Search

Influence of ZrO2 in HfO2 on the reflectance of HfO2\\/SiO2 multilayer at 248nm was investigated. Two kinds of HfO2 with different ZrO2 content were chosen as high refractive index material and the same kind of SiO2 as low refractive index material to prepare the mirrors by electron-beam evaporation. The impurities in two kinds of HfO2 starting coating materials and in

Jingmei Yuan; Lei Yuan; Hongbo He; Kui Yi; Zhengxiu Fan; Jianda Shao

2008-01-01

152

High-stability ultrathin spin-on benzocyclobutene gate dielectric for polymer field-effect transistors  

NASA Astrophysics Data System (ADS)

Using a thermal-crosslinkable siloxane bisbenzocyclobutene, high quality spin-on (solutionprocessable) gate dielectric layers as thin as 50 nm have been fabricated over the semiconductor layer for polymer field-effect transistors. This was demonstrated on a poly(9,9-dialkylfluorene-alt-triarylamine) as p-channel semiconductor, with a surfactantion-exchanged poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate complex as top-gate electrode. The devices operate at a low voltage with a field-effect mobility of few 10-4 cm2/Vs, and can be continuously operated at 120 °C.

Chua, Lay-Lay; Ho, Peter K. H.; Sirringhaus, Henning; Friend, Richard H.

2004-04-01

153

Metal dopants in HfO2-based RRAM: first principle study  

NASA Astrophysics Data System (ADS)

Based on density-functional theory (DFT), the effects of metal dopants in HfO2-based RRAM are studied by the Vienna ab initio simulation package (VASP). Metal dopants are classified into two types (interstitial and substitutional) according to the formation energy when they exist in HfO2 cell. Several conductive channels are observed through the isosurface plots of the partial charge density for HfO2 doped with interstitial metals, while this phenomenon cannot be found in HfO2 doped with substitutional metals. The electron density of states (DOS) and the projected electron density of states (PDOS) are calculated and analyzed; it is found that the conduction filament in HfO2 is directly formed by the interstitial metals and further, that the substitutional metals cannot directly generate conduction filament. However, all the metal dopants contribute to the formation of the oxygen vacancy (VO) filament. The formation energy of the VO and the interaction between metal dopants and VO are calculated; it is revealed that the P-type substitutional metal dopants have a strong enhanced effect on the VO filament, the interstitial metal dopants have a minor assistant effect, while Hf-like and N-type substitutional metal dopants have the weakest assistant effect.

Yuanyang, Zhao; Jiayu, Wang; Jianbin, Xu; Fei, Yang; Qi, Liu; Yuehua, Dai

2014-04-01

154

Thermally-driven H interaction with HfO2 films deposited on Ge(100) and Si(100)  

NASA Astrophysics Data System (ADS)

In the present work, we investigated the thermally-driven H incorporation in HfO2 films deposited on Si and Ge substrates. Two regimes for deuterium (D) uptake were identified, attributed to D bonded near the HfO2/substrate interface region (at 300 °C) and through the whole HfO2 layer (400-600 °C). Films deposited on Si presented higher D amounts for all investigated temperatures, as well as, a higher resistance for D desorption. Moreover, HfO2 films underwent structural changes during annealings, influencing D incorporation. The semiconductor substrate plays a key role in this process.

Soares, G. V.; Feijó, T. O.; Baumvol, I. J. R.; Aguzzoli, C.; Krug, C.; Radtke, C.

2014-01-01

155

Hafnium dioxide gate dielectrics, metal gate electrodes, and phenomena occurring at their interfaces  

Microsoft Academic Search

As metal-oxide-semiconductor field-effect transistor (MOSFET) gate lengths scale down below 45 nm, the gate oxide thickness approaches 1 nm equivalent oxide thickness. At this thickness, conventional silicon dioxide (SiO 2) gate dielectrics suffer from excessive gate leakage. Higher permittivity dielectrics are required to counter the increase in gate leakage. Hafnium dioxide (HfO2) has emerged as a promising dielectric candidate. HfO2

James Kenyon Schaeffer III

2004-01-01

156

Phase diagrams and dielectric response of epitaxial (BaxSr1-x)TiO3 ultrathin films: A first-principles study  

NASA Astrophysics Data System (ADS)

A method based on first-principles calculations was used to construct temperature versus misfit strain phase diagrams for epitaxial (BaxSr1-x)TiO3 ultrathin films over the entire composition range from x=0 to x=1. The predicated phase diagrams show “topologies” that are similar to those calculated by Shirokov et al. (Phy. Rev. B. 79 (2009) 144118), but with quantitative differences that are examined and explained. The dependence of the dielectric permittivity on the misfit strain and the film composition at room temperature are also investigated and compared with available theoretical predications and experimental measurements.

Bin-Omran, S.

2012-09-01

157

Light trapping in ultrathin silicon photonic crystal superlattices with randomly-textured dielectric incouplers.  

PubMed

We report here several different superlattice photonic crystal based designs for 200nm thick c-Si solar cells, demonstrating that these structures have the ability to increase broadband absorption from ? = 300nm to 1100nm by more than 100% compared to a planar cell with an optimized anti-reflection coating. We show that adding superlattices into photonic crystals introduces new optical modes that contribute to enhanced absorption. The greatest improvements are obtained when combining a superlattice photonic crystal with a randomly textured dielectric coating that improves incoupling into the modes of the absorbing region. Finally, we show that our design methodology is also applicable to layers 1 to 4 microns in thickness, where absorbed currents competitive with conventional thick Si solar cells may be achieved. PMID:24514610

Callahan, Dennis M; Horowitz, Kelsey A W; Atwater, Harry A

2013-12-16

158

High-K gate dielectrics  

NASA Astrophysics Data System (ADS)

High-K dielectric thin films have been investigated as alternative gate dielectrics. Our results suggest that single-layer sputtered ZrO2 or HfO2 thin films deposited directly on Si substrate, without the use of a barrier layer, exhibit excellent electrical and reliability characteristics. Equivalent oxide thickness as thin as 9 angstrom with leakage current of about 10-2 A/cm2 was achieved. This is the lowest EOT value ever reported for ZrO2 and HfO2 thin films. Low charge- trapping, high breakdown field, and negligible stress- induced leakage currents have also been obtained.

Qi, Wen-Jie; Lee, Byoung H.; Nieh, Renee; Kang, Laegu; Jeon, Yongjoo; Onishi, Katsu; Lee, Jack C.

1999-09-01

159

HfO2 nanocrystal memory on SiGe channel  

NASA Astrophysics Data System (ADS)

This study proposes a novel HfO2 nanocrystal memory on epi-SiGe (Ge: 15%) channel. Because SiGe has a smaller bandgap than that of silicon, it increases electron/hole injection and the enhances program/erase speeds. This study compares the characteristics of HfO2 nanocrystal memories with different oxynitride tunnel oxide thicknesses on Si and epi-SiGe substrate. Results show that the proposed nonvolatile memory possesses superior characteristics in terms of considerably large memory window for two-bits operation, high speed program/erase for low power applications, long retention time, excellent endurance, and strong immunity to disturbance.

Lin, Yu-Hsien; Chien, Chao-Hsin

2013-02-01

160

Ab initio Study of Metal Interfaces with HfO2 and SiO2: Work Function Modulation  

NASA Astrophysics Data System (ADS)

For the next generation of metal-oxide-semiconductor field-effect transistors (MOSFETs), the suitable metal candidate has to be identified. The choice of a specific metal electrode on high-k gate dielectric oxide films is strongly influenced by the possible interface chemical reactions and defects. In this study, ab initio calculations are employed to investigate and analyze a number of possible interface structures between gate dielectric oxides, HfO2 and SiO2, and metal electrodes. The structural stability and electronic structure of the interfaces with implications to metal work functions are discussed. The work function of metals on oxides is significantly influenced by the interface configurations and by the particular bonding pattern at the interface. For work function modulation, model interface systems of metal bi-layers are constructed based on structural and compositional heterogeneity. It is found that a few atomic layers of the underlying metal shift the work function of bi-layers to that of underlying metal.

Magyari-Köpe, Blanka; Nishi, Yoshio; Colombo, Luigi; Cho, Kyeongjae

2007-03-01

161

Atomic layer deposition of HfO2 thin films using H2O2 as oxidant  

NASA Astrophysics Data System (ADS)

HfO2 films were deposited by atomic layer deposition (ALD) using Hf[(C2H5)(CH3)N]4 and H2O2 at a temperature range of 175–325 °C. The growth per cycle of the HfO2 films decreased with increasing temperature up to 280 °C and then abruptly increased above 325 °C as a result of the thermal decomposition of the precursor. Although the HfO2 films grown with H2O2 exhibited slightly higher carbon contents than those grown with H2O, the leakage properties of the HfO2 films grown with H2O2 were superior to those of the HfO2 films grown with H2O. This is because the HfO2 films grown with H2O2 were fully oxidized as a result of the strong oxidation potential of H2O2. The use of the ALD process with H2O2 also revealed the conformal growth of HfO2 films on a SiO2 hole structure with an aspect ratio of ˜15. This demonstrates that using the ALD process with H2O2 shows great promise for growing robust HfO2 films.

Choi, Min-Jung; Park, Hyung-Ho; Jeong, Doo Seok; Kim, Jeong Hwan; Kim, Jin-Sang; Kim, Seong Keun

2014-05-01

162

The performance and reliability of PMOSFET's with ultrathin silicon nitride\\/oxide stacked gate dielectrics with nitrided Si-SiO2 interfaces prepared by remote plasma enhanced CVD and post-deposition rapid thermal annealing  

Microsoft Academic Search

Ultrathin (~1.9 nm) nitride\\/oxide (N\\/O) dual layer gate dielectrics have been prepared by the remote plasma enhanced chemical vapor deposition (RPECVD) of Si3N4 onto oxides. Compared to PMOSFET's with heavily doped p+-poly-Si gates and oxide dielectrics, devices incorporating the RPECVD stacked nitrides display reduced tunneling current, effectively no boron penetration and improved interface characteristics. By preventing boron penetration into the

Yider Wu; Gerald Lucovsky; Yi-Mu Lee

2000-01-01

163

Thermal Conductivity and Water Vapor Stability of HfO2-based Ceramic Coating Materials  

NASA Technical Reports Server (NTRS)

HfO2-Y2O3 and La2Zr2O7 are candidate thermal/environmental barrier coating materials for gas turbine ceramic matrix composite (CMC) combustor liner applications because of their relatively low thermal conductivity and high temperature capability. In this paper, thermal conductivity and high temperature phase stability of plasma-sprayed coatings and/or hot-pressed HfO2-5mol%Y2O3, HfO2- 15mol%Y2O3 and La2Zr2O7 were evaluated at temperatures up to 1700 C using a steady-state laser heat-flux technique. Sintering behavior of the plasma-sprayed coatings was determined by monitoring the thermal conductivity increases during a 20-hour test period at various temperatures. Durability and failure mechanisms of the HfO2-Y2O3 and La2Zr2O7 coatings on mullite/SiC Hexoloy or CMC substrates were investigated at 1650 C under thermal gradient cyclic conditions. Coating design and testing issues for the 1650 C thermaVenvironmenta1 barrier coating applications will also be discussed.

Zhu, Dongming; Fox, Dennis S.; Bansal, Narottam P.; Miller, Robert A.

2004-01-01

164

Thermal Conductivity and Water Vapor Stability of Ceramic HfO2-Based Coating Materials.  

National Technical Information Service (NTIS)

HfO2-Y2O3 and La2Zr2O7 are candidate thermal/environmental barrier coating materials for gas turbine ceramic matrix composite (CMC) combustor liner applications because of their relatively low thermal conductivity and high temperature capability. In this ...

D. M. Zhu D. S. Fox N. P. Bansal R. A. Miller

2004-01-01

165

Thermal Conductivity and Water Vapor Stability of Ceramic HfO2-Based Coating Materials  

NASA Technical Reports Server (NTRS)

HfO2-Y2O3 and La2Zr2O7 are candidate thermal/environmental barrier coating materials for gas turbine ceramic matrix composite (CMC) combustor liner applications because of their relatively low thermal conductivity and high temperature capability. In this paper, thermal conductivity and high temperature phase stability of plasma-sprayed coatings and/or hot-pressed HfO2-5mol%Y2O3, HfO2-15mol%Y2O3 and La2Zr2O7 were evaluated at temperatures up to 1700 C using a steady-state laser heat-flux technique. Sintering behavior of the plasma-sprayed coatings was determined by monitoring the thermal conductivity increases during a 20-hour test period at various temperatures. Durability and failure mechanisms of the HfO2-Y2O3 and La2Zr2O7 coatings on mullite/SiC Hexoloy or CMC substrates were investigated at 1650 C under thermal gradient cyclic conditions. Coating design and testing issues for the 1650 C thermal/environmental barrier coating applications will also be discussed.

Zhu, Dong-Ming; Fox, Dennis S.; Bansal, Narottam P.; Miller, Robert A.

2004-01-01

166

Electrical Properties of HfO2 Films Formed by Ion Assisted Deposition  

Microsoft Academic Search

In this paper, the electrical and structural analysis of HfO2 thin films formed by ion assisted deposition are reported. The electrical results show excellent layer uniformity and very good reproducibility before post deposition annealing. The influence of the oxygen flow during the growth upon the electrical properties of the film has also been investigated. Forming gas annealing removed the hysteresis

K. Cherkaoui; A. Negara; S. McDonnell; G. Hughes; M. Modreanu; P. K. Hurley

2006-01-01

167

Local elastic modulus of RF sputtered HfO2 thin film by atomic force acoustic microscopy  

NASA Astrophysics Data System (ADS)

Atomic force acoustic microscopy (AFAM) is a useful nondestructive technique for measurement of local elastic modulus of materials at nano-scale spatial resolution by measuring the contact resonance spectra for higher order modes of the AFM cantilever. The elastic modulus of RF sputtered HfO2 thin film has been measured quantitatively, using reference approach in which measurements are performed on the test and reference samples. Using AFAM, the measured elastic modulus of the HfO2 thin film is 223±27 GPa, which is in agreement with the literature value of 220±40 GPa for atomic layer deposited HfO2 thin film using nanoindentation technique.

Jena, S.; Tokas, R. B.; Sarkar, P.; Misal, J. S.; Rao, K. D.; Thakur, S.; Sahoo, N. K.

2014-04-01

168

Femtosecond laser-induced damage of HfO2/SiO2 mirror with different stack structure.  

PubMed

Laser-induced damage of the "standard" (?/4 stack structure) and "modified" (reduced standing-wave field) HfO(2)/SiO(2) mirrors were investigated by a commercial 800 nm Ti:sapphire laser system. Three kinds of pulse duration of 50 fs, 105 fs, and 135 fs were chosen. The results show that the single-shot damage threshold of the "modified" mirror was about 14%-23% higher compared to that of the "standard" mirror. A model based on the rate equation for free electron generation was adopted to explain the threshold results. It took in account the transient changes in the dielectric function of material during the laser pulse. The simulated threshold agreed with the experimental very well. Besides, for two kinds of mirror, typical breakdown craters for both the single-shots and multi-shots damage tests reveal striking distinct characteristics. Interestingly, the multi-shots damage crater with zigzag-like edge was observed only on the "standard" mirror. These phenomena were illustrated reasonably by the distribution features of the electric field intensity within the mirrors. PMID:22945167

Chen, Shunli; Zhao, Yuan'an; Yu, Zhenkun; Fang, Zhou; Li, Dawei; He, Hongbo; Shao, Jianda

2012-09-01

169

Design and control of Ge-based metal-oxide-semiconductor interfaces for high-mobility field-effect transistors with ultrathin oxynitride gate dielectrics  

NASA Astrophysics Data System (ADS)

High-quality Ge-based metal-oxide-semiconductor (MOS) stacks were achieved with ultrathin oxynitride (GeON) gate dielectrics. An in situ process based on plasma nitridation of the base germanium oxide (GeO2) surface and subsequent metal electrode deposition was proven to be effective for suppressing electrical deterioration induced by the reaction at the metal/insulator interface. The electrical properties of the bottom GeON/Ge interface were further improved by both low-temperature oxidation for base GeO2 formation and high-temperature in situ vacuum annealing after plasma nitridation of the base oxide. Based on the optimized in situ gate stack fabrication process, very high inversion carrier mobility (?hole: 445 cm2/Vs, ?electron: 1114 cm2/Vs) was demonstrated for p- and n-channel Ge MOSFETs with Al/GeON/Ge gate stacks at scaled equivalent oxide thickness down to 1.4 nm.

Minoura, Yuya; Kasuya, Atsushi; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji

2013-07-01

170

Morphology and Photoluminescence of HfO2Obtained by Microwave-Hydrothermal  

PubMed Central

In this letter, we report on the obtention of hafnium oxide (HfO2) nanostructures by the microwave-hydrothermal method. These nanostructures were analyzed by X-ray diffraction (XRD), field-emission gum scanning electron microscopy (FEG-SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDXS), ultraviolet–visible (UV–vis) spectroscopy, and photoluminescence (PL) measurements. XRD patterns confirmed that this material crystallizes in a monoclinic structure. FEG-SEM and TEM micrographs indicated that the rice-like morphologies were formed due to an increase in the effective collisions between the nanoparticles during the MH processing. The EDXS spectrum was used to verify the chemical compositional of this oxide. UV–vis spectrum revealed that this material have an indirect optical band gap. When excited with 488 nm wavelength at room temperature, the HfO2nanostructures exhibited only one broad PL band with a maximum at around 548 nm (green emission).

2009-01-01

171

Reversed spin polarization at the Co(001)-HfO2(001) interface  

NASA Astrophysics Data System (ADS)

Ab initio electronic-structure calculations on the Co(001)-HfO2(001) interface are reported. The spin polarization of conduction electrons is positive at the interface, i.e., it is reversed with respect to the spin polarization in bulk Co. The electronic structure is very sensitive to the interface structure; without atomic relaxations the reversed spin polarization is not found. The possible relation with spin-polarized tunneling and magnetoresistance is discussed.

de Boer, P. K.; de Wijs, G. A.; de Groot, R. A.

1998-12-01

172

Change of resistive-switching in TiO2 films with additional HfO2 thin layer  

NASA Astrophysics Data System (ADS)

We have fabricated TiN/(HfO2)/TiO2/Pt/Ti stacks on SiO2/Si substrates and investigated the characteristics of the bipolar resistive switching of those stacks. Compared to the single TiO2 structure, more stable bipolar switching in the current-voltage curve was accomplished in the HfO2/TiO2 structure. We obtained a smaller range of SET variation, a larger sensing margin, and higher resistance values of the high-resistance state with an additional HfO2 layer. Especially, in the case of the HfO2/TiO2 structure, the set voltage was decreased after O2 annealing. The heat treatment in an ambient of O2 and an additional HfO2 layer can improve the bipolar resistive switching behavior for resistive random access memory applications.

Lee, Doosung; Sung, Yonghun; Sohn, Hyunchul; Ko, Dae-Hong; Cho, Mann-Ho

2012-05-01

173

Effects of Thermal Treatments on the Trapping Properties of HfO2 Films for Charge Trap Memories  

NASA Astrophysics Data System (ADS)

The charge trapping properties of HfO2 thin films for application in charge trap memories are investigated as a function of high-temperature postdeposition annealing (PDA) and oxide thickness in the TaN/Al2O3/HfO2/SiO2/Si structure. The trap density (NT) in HfO2, extracted by simulating the programming transient, is in the 1019--1020 cm-3 range, and it is related to film thickness and PDA temperature. Diffusion phenomena in the stack play a significant role in modifying NT in HfO2 and the insulating properties of the Al2O3 layer. The memory performances for 1030 °C PDA are promising with respect to standard stacks featuring Si3N4.

Spiga, Sabina; Driussi, Francesco; Lamperti, Alessio; Congedo, Gabriele; Salicio, Olivier

2012-02-01

174

Higher permittivity rare earth doped HfO2 for sub-45-nm metal-insulator-semiconductor devices  

NASA Astrophysics Data System (ADS)

Rare earth (RE) doping (Gd, Er, Dy) of HfO2 reduces leakage current by three orders of magnitude compared with pure HfO2. The key to reducing HfO2 leakage current and equivalent oxide thickness (EOT) is stabilization of the higher permittivity tetragonal phase. RE doping of 10-20 at. % stabilizes tetragonal HfO2 and increases permittivity. The maximum permittivity achieved for HfREOx is 28. The maximum permittivity for ZrREO is 32. HfGdO metal-insulator-semiconductor capacitors with EOT=1.93 nm and leakage current <1×10-8 A/cm2 after 1070 °C have been demonstrated.

Govindarajan, S.; Böscke, T. S.; Sivasubramani, P.; Kirsch, P. D.; Lee, B. H.; Tseng, H.-H.; Jammy, R.; Schröder, U.; Ramanathan, S.; Gnade, B. E.

2007-08-01

175

The effect of thickness and loading force on wear behavior of HfO2  

NASA Astrophysics Data System (ADS)

The effect of annealing treatment on hafnium oxide (HfO2) thin films with two thicknesses (20 and 50 nm) has been observed. The surface morphology and tribological properties of HfO2 thin films were measured through atomic force microscopy (AFM). It is found that annealing treatment and increasing thickness of thin film would promote the formation and growth of island-like grains, which contributes a raise in surface roughness. During scratch test, plowing behavior dominated the deformation mechanism in the form of lumps along the edge of grooves by AFM-3D images. Besides, slower scratch speed led to larger deformation energy and caused a serious fracture. The annealing-induced crystallization resulted in reduced penetration depth and coefficient of friction (COF). The varied COF with respect to different normal forces reflected substrate effect. The thicker HfO2 films exhibited better wear resistance regardless of annealing conditions. It is because that increase in film thickness accompanied growth of polycrystalline structure.

He, B.-C.; Fu, W.-E.; Chang, Y.-Q.; Liou, H.-C.

2014-03-01

176

Normally-off HfO2-gated diamond field effect transistors  

NASA Astrophysics Data System (ADS)

A normally-off hydrogenated-diamond (H-diamond) field effect transistor (FET) using a HfO2 gate oxide is demonstrated. The HfO2 gate oxide has a bilayer structure which is fabricated by a sputter-deposition (SD) technique on a thin buffer layer prepared by an atomic layer deposition (ALD) technique. The role of the ALD-HfO2 is found to prevent deterioration of the H-diamond surface by the SD process. The leakage current density of the SD-HfO2/ALD-HfO2/H-diamond structure is smaller than 1.1 × 10-4 A cm-2 at gate voltages from -9.0 to 2.0 V. The capacitance-voltage characteristic shows that fixed and trapped charge densities are low enough to operate the FET. The HfO2-gated FET has p-type channel and complete normally-off characteristics. The drain-source current maximum, threshold voltage, extrinsic transconductance maximum, and effective mobility of the FET with gate length of 4 ?m are -37.6 mA mm-1, -1.3 +/- 0.1 V, 11.2 +/- 0.1 mS mm-1, and 38.7 +/- 0.5 cm2 V-1 s-1, respectively.

Liu, J. W.; Liao, M. Y.; Imura, M.; Koide, Y.

2013-08-01

177

Growth and phase stabilization of HfO 2 thin films by ALD using novel precursors  

NASA Astrophysics Data System (ADS)

HfO 2 thin films were grown at temperatures between 250 and 400 °C by atomic layer deposition using novel cyclopentadienyl-alkylamido precursors, namely CpHf(NMe 2) 3 and (CpMe)Hf(NMe 2) 3 (Cp, cyclopentadienyl=C 5H 5). Ozone was used as the oxygen source. The self-limiting growth mode was verified at 300 °C with a growth rate of 0.7-0.8 Å/cycle, depending on the precursor. Thermal decomposition started to have an effect on the growth mechanism at temperatures near 350 °C. As compared to the widely applied Hf(NEtMe) 4 precursor, these novel precursors with higher thermal stability resulted in HfO 2 films with lower impurity contents. The carbon and hydrogen contents below 0.5 and 1.0 at.%, respectively, were characterized for films deposited at 300 °C from both novel precursors. The 50-nm-thick HfO 2 films deposited at 300 °C or above were crystallized in mixture of monoclinic and cubic or tetragonal phases. Doping with low amounts of yttrium and subsequent annealing of 7-nm-thick film on TiN stabilized the preferred high-permittivity cubic or tetragonal phases, resulting in low capacitance equivalent thickness and leakage current density.

Niinistö, Jaakko; Mäntymäki, Miia; Kukli, Kaupo; Costelle, Leila; Puukilainen, Esa; Ritala, Mikko; Leskelä, Markku

2010-01-01

178

Resistive switching of HfO 2-based metal-insulator-metal diodes: Impact of the top electrode material  

Microsoft Academic Search

This paper deals with the impact of the top metal electrode on the resistive switching properties of HfO2-based Metal\\/Insulator\\/Metal diodes. By screening five different metals as top electrode, Al-Cu-Hf-Pt-Ti, we have demonstrated the feasibility of the resistive switching effect on HfO2. Metals with a low enthalpy of formation of oxides ?Hf0 (Pt and Cu) lead to unipolar switching whereas easily

T. Bertaud; D. Walczyk; Ch. Walczyk; S. Kubotsch; M. Sowinska; T. Schroeder; Ch. Wenger; C. Vallée; P. Gonon; C. Mannequin; V. Jousseaume; H. Grampeix

179

Electronic structure of GeO2-passivated interfaces of (100)Ge with Al2O3 and HfO2  

NASA Astrophysics Data System (ADS)

Analysis of internal photoemission and photoconductivity in Ge/thermal germanium oxide/high-dielectric constant oxide (HfO2,Al2O3) structures reveals that the bandgap of the germanium oxide interlayer is significantly lower (4.3+/-0.2 eV) than that of stiochiometric GeO2 (5.4-5.9 eV). As a result, the conduction and valence band offsets at the interface appear to be insufficient to block electron and hole injection leading to significant charge trapping in the GeOx/high-? oxide stack. Formation of a hydroxyl-rich Ge oxide phase is suggested to be responsible for the modification of the oxide properties.

Afanas'ev, V. V.; Stesmans, A.; Delabie, A.; Bellenger, F.; Houssa, M.; Meuris, M.

2008-01-01

180

Surface and interfacial reaction study of half cycle atomic layer deposited HfO2 on chemically treated GaSb surfaces  

NASA Astrophysics Data System (ADS)

An in situ half-cycle atomic layer deposition/X-ray photoelectron spectroscopy (XPS) study was conducted in order to investigate the evolution of the HfO2 dielectric interface with GaSb(100) surfaces after sulfur passivation and HCl etching, designed to remove the native oxides. With the first pulses of tetrakis(dimethylamido)hafnium(IV) and water, a decrease in the concentration of antimony oxide states present on the HCl-etched surface is observed, while antimony sulfur states diminished below the XPS detection limit on sulfur passivated surface. An increase in the amount of gallium oxide/sulfide is seen, suggesting oxygen or sulfur transfers from antimony to gallium during antimony oxides/sulfides decomposition.

Zhernokletov, D. M.; Dong, H.; Brennan, B.; Yakimov, M.; Tokranov, V.; Oktyabrsky, S.; Kim, J.; Wallace, R. M.

2013-04-01

181

Vox/Eox-Driven Breakdown of Ultrathin SiON Gate Dielectrics in p-Type Metal Oxide Semiconductor Field Effect Transistors under Low-Voltage Inversion Stress  

NASA Astrophysics Data System (ADS)

The breakdown mechanism of ultrathin SiON gate dielectrics in p-type metal oxide semiconductor field effect transistors having p+gates (p+gate-pMOSFETs) has been studied. Systematic study with varying gate doping concentrations has revealed that, in the case of p+gate-pMOSFET in inversion mode, gate dielectric breakdown under stress voltage lower than -4 V is driven by oxide voltage (Vox) or oxide field (Eox), while the breakdown under stress voltage higher than -4 V is driven by gate voltage (Vg). The Vox/Eox-driven breakdown observed under low stress voltage is quite important to the reliability of low-voltage complementary metal oxide semiconductor (CMOS). By studying the mechanism of the breakdown, it has been clarified that the breakdown is not induced by electron current. The concept that the breakdown is due to same mechanism as the negative bias temperature instability (NBTI), namely the interfacial hydrogen release driven by Eox, has been shown to be possible. However, direct tunneling of holes driven by Vox has also been found to be a possible driving force of the breakdown. Although a decisive conclusion concerning the mechanism issue has not yet been obtained, the key factor that governs the breakdown has been shown to be Vox or Eox.

Tsujikawa, Shimpei; Shiga, Katsuya; Umeda, Hiroshi; Yugami, Jiro

2007-01-01

182

Effects of deuterium anneal on MOSFETs with HfO2 gate dielectrics  

Microsoft Academic Search

The effects of high-temperature (600°C) anneal in a dilute deuterium (N2 : D2= 96 : 4) atmosphere was first investigated and evaluated in comparison to high-temperature forming gas (N2 : H2= 96 : 4) anneal (600°C) and nonanneal samples. The high-temperature deuterium anneal was as effective as the forming gas anneal in improving MOSCAP and MOSFET characteristics such as the

Rino Choi; Katsunori Onishi; Chang Seok Kang; Hag-Ju Cho; Y. H. Kim; Siddharth Krishnan; M. S. Akbar; Jack C. Lee

2003-01-01

183

Dielectric properties of dysprosium- and scandium-doped hafnium dioxide thin films  

Microsoft Academic Search

Dysprosium- and scandium-doped HfO2 films have been deposited by atomic-vapor deposition on SiO2\\/Si substrates. Glancing-incidence x-ray diffraction demonstrates that Dy0.10Hf0.90Ox and Sc0.10Hf0.90Ox films show a cubic crystal structure, whereas HfO2 films are monoclinic. The dielectric permittivity increases strongly from 16 for HfO2 to 32 for Dy0.10Hf0.90Ox and Sc0.10Hf0.90Ox. This leads to a reduction of the leakage current in the tunneling

C. Adelmann; V. Sriramkumar; S. van Elshocht; P. Lehnen; T. Conard; S. de Gendt

2007-01-01

184

XRD and EXAFS studies on the structure of Er3+-doped SiO2-HfO2 glass-ceramic waveguides: Er3+-activated HfO2 nanocrystals  

NASA Astrophysics Data System (ADS)

This paper describes the structure of Er3+-doped SiO2-HfO2 waveguides containing nanocrystals of HfO2. Pure and 1 mol% Er3+-doped 70SiO2-30HfO2 films were deposited by the sol-gel method on amorphous SiO2 substrates using the dip-coating technique. Each waveguide has experienced a single thermal treatment at temperatures ranging from 900 to 1200 °C, for either short (30 min) or long (24 h) durations. Crystallization and microstructure were studied by x-ray diffraction (XRD). The local environments of hafnium and erbium ions were determined, respectively, from Hf and Er L3-edges extended x-ray absorption fine structure (EXAFS) experiments. Both XRD and EXAFS results demonstrate the substitution of Hf4+ by Er3+ ions in the crystalline structure. XRD shows the nucleation of tetragonal HfO2 nanocrystals after heat treatment at 1000 °C for 30 min in the pure waveguide, and at 900 °C for 24 h in the waveguide doped with Er3+. In both series, partial transformation from tetragonal to monoclinic HfO2 nanocrystals starts after heat treatment at 1100 °C for 24 h. The average crystallite size and size distribution can be controlled by thermal annealing temperature and duration, respectively, with brief treatment yielding a more homogeneous nanocrystal size.

Afify, N. D.; Dalba, G.; Rocca, F.

2009-06-01

185

Rotational spectrum of jet-cooled HfO2 and HfO  

NASA Astrophysics Data System (ADS)

The rotational spectrum of jet-cooled hafnium dioxide obtained by laser ablation of a solid ceramic rod has been investigated by Fourier-transform microwave spectroscopy in the 8 to 28 GHz frequency range. Rotational transitions within the ground and several excited vibrational states of the lowest vibrational mode of the molecule have been assigned. The resulting spectra have been fit, yielding rotational parameters for the five most abundant isotopomers of HfO2. Centrifugal distortion effects are noticeable even for the lowest-J transitions. Very large quadrupole coupling effects for the isotopomers with nuclear quadrupole moments (179Hf (I=9/2) and 177Hf (I=7/2)) have been accounted for using the diagonal elements of the nuclear quadrupole coupling tensor. A ground-state effective C2v geometry has been obtained for HfO2, yielding ro(Hf-O)=1.7764(4) Å and angupr (O-Hf-O)=107.51(1)°. The electric dipole moment has been determined for 180HfO2 from Stark-effect measurements, giving ?=26.42(3)×10-30C.m [7.92(1) D]. Ab initio calculations using density functional theory and relativistic core potentials are in satisfactory agreement with the experimental results. Finally, in the course of this investigation, the rotational spectrum of the diatomic molecule, HfO, has also been reexamined, and new results for vibrational satellites (up to v=18 in some cases) of the J=1<--0 rotational transition are reported. A vibrational analysis using Le Roy's form of the Dunham expansion has allowed the determination of atomic mass-dependent Born-Oppenheimer breakdown parameters for both atoms of HfO.

Lesarri, Alberto; Suenram, R. D.; Brugh, Dale

2002-12-01

186

Characterization of nanostructured HfO 2 films using RBS and PAC  

NASA Astrophysics Data System (ADS)

The hyperfine field at 181Ta lattice sites in a nanostructured HfO 2 thin film doped with Fe was studied using Rutherford Backscattering Spectrometry and Perturbed Angular Correlation techniques. The 409 nm Hf film was deposited by Electron Beam Evaporation on a silicon substrate. The radioactive 181Hf ions were produced by neutron activation of the nanofilm in the Brazilian Research Reactor (IPEN IEA-R1) by the reaction 180Hf(n,?) 181Hf. These studies provided an excellent opportunity to obtain unique information regarding local arrangement of the grains, structure, phase transformations of nanoparticles and interfaces of nanostructured materials and the thin film.

Cavalcante, F. H. M.; Gomes, M. R.; Carbonari, A. W.; Pereira, L. F. D.; Rossetto, D. A.; Costa, M. S.; Alves, E.; Barradas, N. P.; Franco, N.; Redondo, L. M.; Lopes, A. M. L.; Soares, J. C.

2012-02-01

187

Characterization of nanostructured HfO2 films using Perturbed Angular Correlation (PAC) technique  

NASA Astrophysics Data System (ADS)

The hyperfine field at 181Ta lattice sites in nanostructured HfO2 thin films was studied by the Perturbed Angular Correlation (PAC) technique. Thin oxide films were deposited by Electron Beam Evaporation on a silicon substrate. The thickness of the films was ~100 nm and ~250 nm. Radioactive 181Hf nuclei were produced by neutron activation of the film samples in the Brazilian Research Reactor (IPEN IEA-R1) by the reaction 180Hf(n, ?)181Hf. PAC measurements were carried out after annealing at 1473 K. The PAC technique allows the determination of the electric field gradient (EFG) at the probe sites.

Cavalcante, F. H. M.; Gomes, M. R.; Carbonari, A. W.; Pereira, L. F. D.; Rossetto, D. A.; Costa, M. S.; Redondo, L. M.; Mestnik-Filho, J.; Saxena, R. N.; Soares, J. C.

2010-06-01

188

Three-state resistive switching in HfO2-based RRAM  

NASA Astrophysics Data System (ADS)

We investigate the reset transition of HfO2-based RRAM structures with emphasis on revealing three-state resistive switching effects. We study nonpolar switching in Pt/HfO2/Pt and unipolar/bipolar switching in Pt/Ti/HfO2/Pt structures, respectively. However, three-state resistive switching is only confirmed in the former case by means of various reset methodologies. Using two-step reset experiments it is shown that the transition to the complete reset state occurs at higher voltages if the CF first drops to the intermediate state.

Lian, Xiaojuan; Miranda, Enrique; Long, Shibing; Perniola, Luca; Liu, Ming; Suñé, Jordi

2014-08-01

189

Electrical properties of hafnium oxide gate dielectric deposited by plasma enhanced chemical vapor deposition  

Microsoft Academic Search

Hafnium oxide thin films were deposited at 300°Con p-Si (100) substrates by plasma enhanced chemical vapor deposition (PECVD). The gate dielectric formed by PECVD was HfO2\\/SiO2\\/Si structure. The thickness of the HfO2 thin films decreases with increasing. RTA temperature because of its high density. The Pt\\/HfO2\\/SiO2\\/Si structure showed accumulation, depletion and inversion. After the RTA treatment, the capacitances of the

Kyu-Jeong Choi; Woong-Chul Shin; Jong-Bong Park; Soon-Gil Yoon

2001-01-01

190

Characteristics and Reliability of Hafnium Oxide Dielectric Stacks With Room Temperature Grown Interfacial Anodic Oxide  

Microsoft Academic Search

Hafnium oxide dielectric stacks with anodic oxide interfacial layer (ANO-IL) were investigated under low-temperature consideration. A tilted-substrate sputtering technique, which provides various film thicknesses in one processing step, was proposed and useful for the characterization of charge distribution. It was found that charges existed in the HfO2\\/ANO-IL were smaller than that in HfO2\\/rapid-thermal-oxidation IL. The prepared samples exhibit good electrical

Chia-Hua Chang; Jenn-Gwo Hwu

2009-01-01

191

Size control of highly ordered HfO2 nanotube arrays and a possible growth mechanism  

NASA Astrophysics Data System (ADS)

Highly ordered HfO2 nanotube arrays were prepared through an electrochemical anodization in the presence of NH4F and ethylene glycol. The voltage-dependent pore size, wall thickness and porosity were studied using scanning electron microscopy and a wall thickness to pore size ratio was proposed on the basis of the results to serve as a boundary condition additional to the 10% porosity rule introduced by the Gosele group. The average distributions of the tube sizes and wall thicknesses of the nanotubes prepared at 20 V were determined from the small-angle x-ray scattering data using a simple polydisperse core-shell cylinder model fit. Temperature-dependent x-ray diffraction measurements show that the as-grown amorphous nanotube arrays can be converted into crystalline nanotube arrays at a temperature above 500 °C. Transmission electron microscopy study of the dimple layer under the as-grown nanotube arrays reveals the presence of a layer of ordered HfO2 nanocrystals. Further microscopic investigation of the nanotube root region indicates that the nanotubes develop from bulbs produced during anodization. A possible gas bubble initiated growth mechanism based on these observations was proposed.

Qiu, Xiaofeng; Howe, Jane Y.; Cardoso, Mateus B.; Polat, Ozgur; Heller, William T.; Parans Paranthaman, M.

2009-11-01

192

Stress and environmental shift characteristics of HfO2/SiO2 multilayer coatings  

NASA Astrophysics Data System (ADS)

HfO2/SiO2 polarizer coatings for 1054 nm have been produced that have low stress at explicit environmental conditions without the employment of backside stress- compensation films. In this process hafnia is condensed from a metallic melt and silica from an oxide source, both via electron-beam evaporation. Specifically, this process has been adopted for multilayer designs with stringent requirements on spectral control and wavefront distortion. Efforts to meet these requirements have prompted various investigations of coating stress and spectral behavior, especially under changing environmental conditions. Results have shown that coating stress and optical thickness vary significantly with humidity. THese quantities have been measured under both ambient air and dry nitrogen atmospheres. The effects of coating parameters on stress and environmental stability have been examined for an experimental hafnia/silica polarizer coating. The aforementioned parameters are hafnia deposition rate, oxygen pressure during hafnia deposition, and oxygen pressure during silica deposition. Results indicate a strong correlation of coating stress to oxygen pressure during the silica evaporation. Data on the aging of stress in hafnia/silica coatings will also be presented. The HfO2/SiO2 process has ben utilized in high-laser-damage- threshold coatings for the OMEGA laser system and for National Ignition Facility development coatings at the Laboratory for Laser Energetics.

Anzellotti, J. F.; Smith, Douglas J.; Sczupak, Robert J.; Chrzan, Z. Roman

1997-05-01

193

Tunneling-assisted Poole-Frenkel conduction mechanism in HfO2 thin films  

NASA Astrophysics Data System (ADS)

Tunneling-assisted Poole-Frenkel (TAPF) mechanism, which represents electron tunneling from a metal electrode to traps in a nearby insulator layer followed by detrapping of the electrons from the traps by virtue of a lowered potential well due to an applied electric field, is suggested in this study to precisely describe the electrical conduction behavior of a Pt/HfO2/Si capacitor. The current density versus the applied electric-field curves of the TAPF conduction show a similar electric-field dependency to that of the Poole-Frenkel (PF) conduction. However, unlike the PF mechanism, the activation energy of the leakage current density corresponds to the value of the Schottky barrier height (SBH) of a metal/insulator junction minus a lowered potential-well height by the applied electric field in the TAPF mechanism. In addition, the SBH of the Pt/HfO2 junction is calculated considering a high space-charge density (>~1018 cm-3) in the HfO2 layer. The measured activation energy for the electrical conduction from an atomic-layer-deposited HfO2 film is compared to the value that is expected from this model.

Jeong, Doo Seok; Hwang, Cheol Seong

2005-12-01

194

A chemical mechanism for nitrogen incorporation into HfO 2 ALD films using ammonia and alkylamide as precursors  

NASA Astrophysics Data System (ADS)

An atomistic mechanism for the incorporation of nitrogen into HfO 2 ALD films grown using Hf[N(CH 3) 2] 4 and NH 3 was investigated using density functional theory. We find a ligand-exchange mechanism similar to those thought to occur in the ALD of other metal oxide films. Both half-reactions form intermediates that are more stable than the products, have larger barriers than for reaction between H 2O and Hf[N(CH3)2]x? and will thus be significantly slower at ALD temperatures. Therefore water must be purged from the chamber when depositing Hf nitrides or incorporating N into HfO 2 using this chemistry. These results indicate that NH 3 and Hf[N(CH 3) 2] 4 can be used to either incorporate N into HfO 2 ALD films or grow hafnium nitride.

Xu, Ye; Musgrave, Charles B.

2005-10-01

195

Influence of negative ion element impurities on laser induced damage threshold of HfO 2 thin film  

NASA Astrophysics Data System (ADS)

Negative ion element impurities breakdown model in HfO 2 thin film was reported in this paper. The content of negative ion elements were detected by glow discharge mass spectrum analysis (GDMS); HfO 2 thin films were deposited by the electron-beam evaporation method. The weak absorption and laser induced damage threshold (LIDT) of HfO 2 thin films were measured to testify the negative ion element impurity breakdown model. It was found that the LIDT would decrease and the absorption would increase with increasing the content of negative ion element. These results indicated that negative ion elements were harmful impurities and would speed up the damage of thin film.

Wu, ShiGang; Tian, GuangLei; Xia, ZhiLin; Shao, JianDa; Fan, ZhengXiu

2006-11-01

196

Electronic properties of InP (001)/HfO2 (001) interface: Band offsets and oxygen dependence  

NASA Astrophysics Data System (ADS)

Using ab-initio methods, atomic structures and electronic properties of InP (001)/HfO2 (001) interface are studied within the framework of density functional theory. We examine the InP/HfO2 model interface electronic structures under varying oxidation conditions. The effects of indium and phosphorous concentrations on interfacial bonding, defect states, band offsets, and the thermodynamic stability at the interface are also investigated. The origin of interfacial gap states in InP (001)/HfO2 (001) interface are proposed, mainly from the P-rich oxides, which is validated by our experimental work. This highlights the importance of surface passivation prior to high-? deposition based on the in situ spectroscopic results of atomic layer deposition of HfO2 on InP.

KC, Santosh; Dong, Hong; Longo, Roberto C.; Wang, Weichao; Xiong, Ka; Wallace, Robert M.; Cho, Kyeongjae

2014-01-01

197

First-Principles Calculations of Structural, Elastic and Electronic Properties of Tetragonal HfO2 under Pressure  

NASA Astrophysics Data System (ADS)

Structural, elastic and electronic properties of tetragonal HfO2 at applied hydrostatic pressure up to 50 GPa have been investigated using the plane-wave ultrasoft pseudopotential technique based on the first-principles density-functional theory (DFT). The calculated ground-state properties are in good agreement with previous theoretical and experimental data. Six independent elastic constants of tetragonal HfO2 have been calculated at zero pressure and high pressure. From the obtained elastic constants, the bulk, shear and Young's modulus, Poisson's coefficients, acoustic velocity and Debye temperature have been calculated at the applied pressure. Band structure shows that tetragonal HfO2 is an indirect band gap. The variation of the gap versus pressure is well fitted to a quadratic function.

Liu, Qi-Jun; Liu, Zheng-Tang; Feng, Li-Ping

2011-10-01

198

Low temperature atomic layer deposited HfO2 film for high performance charge trapping flash memory application  

NASA Astrophysics Data System (ADS)

The impact of key process parameters on the electrical characteristics of atomic layer deposited HfO2 films has been systematically studied with MHOS devices via capacitance-voltage (C-V) measurement. C-V hysteresis curves revealed that charge storage capacity is significantly enhanced with decreasing substrate temperature from 350 down to 150 °C and/or increasing purge time of the inert gas. The developed HfO2 trapping layer was also demonstrated by a MAHOS memory device. Improved memory window, fast program speed and good retention characteristics have been obtained. The study provides a reference for memory performance improvement of HfO2-based charge trap flash memory.

Chen, Guoxing; Huo, Zongliang; Jin, Lei; Zhang, Dong; Zhao, Shengjie; Han, Yulong; Liu, Su; Liu, Ming

2014-04-01

199

Structural and stoichiometric change in nitrided HfO2 grown on Ge(100) by atomic layer deposition  

NASA Astrophysics Data System (ADS)

The electronic structure and stoichiometric characteristics of postnitrided HfO2 grown on Ge(100) were investigated by various physical measurements. N incorporation in HfO2 grown on Ge was strongly related to the diffusion of Ge from Ge substrate into the film by the postannealing treatment in an NH3 ambient. The diffusion of Ge into the HfO2 film was influenced by the formation of GeOx and GeOxNy in the interfacial region. The small amount of N was incorporated into the film at a nitrided temperature of 600 °C, while much larger amounts of N atoms were incorporated into the interfacial layer to form GeON at a temperature of 700 °C, resulting in the suppression of the diffusion of Ge into the film. However, the interfacial nitrided layer was not stably maintained during the postnitridation anneal, resulting in an enhanced interdiffusion of Ge and Hf into the film.

Chung, K. B.; Whang, C. N.; Cho, M.-H.; Ko, D.-H.

2006-03-01

200

Engineering high dielectric constant materials on silicon carbide  

Microsoft Academic Search

The high dielectric constant (high-kappa) materials of hafnium oxide (HfO2) and aluminum oxide (Al2O3) were grown by atomic layer deposition (ALD) and investigated for integration as gate dielectrics in silicon carbide (SiC) power metal-oxide-semiconductor field-effect transistors (MOSFETs). Smooth HfO2 films were grown on 4H-SiC at temperatures of 200-300°C at a deposition rate of 1-2 A\\/cycle. A temperature-dependent phase transition from

Carey Marie Tanner

2007-01-01

201

Dielectric functions and optical bandgaps of high-K dielectrics for metal-oxide-semiconductor field-effect transistors by far ultraviolet spectroscopic ellipsometry  

Microsoft Academic Search

A far ultraviolet (UV) spectroscopic ellipsometer system working up to 9 eV has been developed, and applied to characterize high-K-dielectric materials. These materials have been gaining greater attention as possible substitutes for SiO2 as gate dielectrics in aggressively scaled silicon devices. The optical properties of four representative high-K bulk crystalline dielectrics, LaAlO3, Y2O3-stabilized HfO2 (Y2O3)0.15-(HfO2)0.85, GdScO3, and SmScO3, were investigated

Seung-Gu Lim; Stas Kriventsov; Thomas N. Jackson; J. H. Haeni; D. G. Schlom; A. M. Balbashov; R. Uecker; P. Reiche; J. L. Freeouf; G. Lucovsky

2002-01-01

202

Electrical and reliability characteristics of ultrathin oxynitride gate dielectric prepared by rapid thermal processing in N2O  

Microsoft Academic Search

The electrical and physical characteristics of oxynitride grown in N2O gas ambient have been studied. The dielectric growth rate in N2O was found to be highly controllable and lower than that in O2. Auger electron spectroscopy studies of oxynitride show a nitrogen-rich layer near the Si-SiO2 interface. Compared with the control oxide, the oxynitride shows excellent electrical characteristics such as

H. Hwang; W. Ting; D.-L. Kwong; J. Lee

1990-01-01

203

High quality ultra thin CVD HfO2 gate stack with poly-Si gate electrode  

Microsoft Academic Search

We have developed and demonstrated an in-situ rapid thermal CVD (RTCVD) process for the fabrication of high quality ultra thin CVD HfO 2 gate stack that is compatible with conventional self-aligned poly-Si gate technology. These poly-Si gated HfO2 gate stack show excellent interface properties, EOT=10.4 Å, and leakage current Jg=0.23 mA\\/cm2 @Vg=-1 V which is several orders of magnitude lower

S. J. Lee; H. F. Luan; W. P. Bai; C. H. Lee; T. S. Jeon; Y. Senzaki; D. Roberts; D. L. Kwong

2000-01-01

204

Hafnium dioxide gate dielectrics, metal gate electrodes, and phenomena occurring at their interfaces  

NASA Astrophysics Data System (ADS)

As metal-oxide-semiconductor field-effect transistor (MOSFET) gate lengths scale down below 45 nm, the gate oxide thickness approaches 1 nm equivalent oxide thickness. At this thickness, conventional silicon dioxide (SiO 2) gate dielectrics suffer from excessive gate leakage. Higher permittivity dielectrics are required to counter the increase in gate leakage. Hafnium dioxide (HfO2) has emerged as a promising dielectric candidate. HfO2 films deposited using metal organic chemical vapor deposition are being studied to determine the impact of process and annealing conditions on the physical and electrical properties of the gate dielectric. This study indicates that deposition and annealing temperatures influence the microstructure, density, impurity concentration, chemical environment of the impurities, and band-gap of the HfO2 dielectric. Correlations of the electrical and physical properties of the films indicate that impurities in the form of segregated carbon clusters, and low HfO2 density are detrimental to the leakage properties of the gate dielectric. Additionally, as the HfO2 thickness scales, the additional series capacitance due to poly-silicon depletion plays a larger roll in reducing the total gate capacitance. To solve this problem, high performance bulk MOSFETs will require dual metal gate electrodes possessing work functions near the silicon band edges for optimized drive current. This investigation evaluates TiN, Ta-Si-N, Ti-Al-N, WN, TaN, TaSi, Ir and IrO2 electrodes as candidate electrodes on HfO2 dielectrics. The metal-dielectric compatibility was studied by annealing the gate stacks at different temperatures. The physical stability and effective work functions of metal electrodes on HfO2 are discussed. Finally, Fermi level pinning of the metal is a barrier to identifying materials with appropriate threshold voltages. The contributions to the Fermi level pinning of platinum electrodes on HfO2 gate dielectrics are investigated by examining the impact of oxygen and forming gas anneals on the effective work function of platinum-HfO2-silicon capacitors. Oxygen anneals result in higher effective work functions for platinum on HfO 2 than forming gas anneals. The presence of interfacial oxygen vacancies or Pt-Hf bonds is believed to be responsible for a degree of pinning that is stronger than predicted from the metal induced gap states model alone.

Schaeffer, James Kenyon, III

205

Thermal stability and electrical properties of titanium-aluminum oxide ultrathin films as high-k gate dielectric materials  

Microsoft Academic Search

As potential high-k gate dielectric material for metal-oxide-semiconductor field effect transistor, the TiO2 incorporated Al2O3 [(TiO2)x(Al2O3)1-x (TAO)] films have been prepared by pulsed laser deposition. The thermal stability and electrical properties of the TAO films annealed at different temperatures have been systematically investigated by x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and capacitance-voltage measurements. These results show that the TAO

L. Shi; Y. D. Xia; B. Xu; J. Yin; Z. G. Liu

2007-01-01

206

Investigation of interaction between graphene and dielectrics  

Microsoft Academic Search

The properties of micromechanically exfoliated graphene on different oxide dielectrics--- SiO2, Al2O3, and HfO2---are investigated by Raman spectroscopy and AFM measurement. The pristine graphene has stronger adhesion and a higher hole concentration when the dielectric constant of the underlying oxide is higher. It is found that annealing under a high vacuum significantly enhances the adhesion between graphene and the oxides

Seung Min Song; Byung Jin Cho

2010-01-01

207

Investigation of interaction between graphene and dielectrics  

Microsoft Academic Search

The properties of micromechanically exfoliated graphene on different oxide dielectrics— SiO2, Al2O3, and HfO2—are investigated by Raman spectroscopy and AFM measurement. The pristine graphene has stronger adhesion and a higher hole concentration when the dielectric constant of the underlying oxide is higher. It is found that annealing under a high vacuum significantly enhances the adhesion between graphene and the oxides

Seung Min Song; Byung Jin Cho

2010-01-01

208

Electron Hole Mobility in HfO2, ZrO2, and ThO2.  

National Technical Information Service (NTIS)

Electrical conductivity is combined with either thermogravimetric or Seebeck coefficient data to obtain as estimate of the electron hole drift mobility in HfO2, ZrO2 and ThO2. The absence of an observable weight change with changing oxygen pressure in ZrO...

J. M. Wimmer N. M. Tallan

1971-01-01

209

Process development, material analysis, and electrical characterization of ultra thin hafnium silicate films for alternative gate dielectric application  

NASA Astrophysics Data System (ADS)

As aggressive scaling of the Metal-Oxide-Semiconductor (MOS) integrated circuit continues, the required equivalent oxide thickness (EOT) for 100nm technology and beyond is expected to be less than 12A. In this ultra-thin film regime, SiO2 or oxynitrides face serious limitations due to direct tunneling currents, dopant penetration, and reliability concerns. HfO 2, ZrO2 and their silicates are being considered as potential candidates for replacing conventional oxides or oxynitrides owing to their thermodynamic stability in contact with silicon, high dielectric constants, chemical stability at high temperatures, etc. Although HfO 2 has shown promising electrical characteristics such as low EOT and leakage, low crystallization temperature, poor interface quality, uncontrolled interfacial layer growth, and reliability issues are some of the concerns with it. HfSixOy has been sought as a solution to alleviate some of these problems. Hafnium silicate films were deposited by co-sputtering of hafnium and silicon in argon ambient followed by annealing. Hafnium silicates with more than 13% Si remains amorphous even after 1000°C anneals. They also show better thermal stability characteristics than HfO2 at all compositions studied. They have been shown to be compatible with poly and TaN gate electrodes. Through process optimization, Hf-silicate films have been scaled down to 10.3A, with leakage in the order of 1mA/cm2 at -1.5V. Low dispersion, low stress-induced leakage currents, high effective breakdown fields, and large lifetimes were obtained. Good thermal stability with polysilicon and TaN electrodes were also obtained. MOS transistors have been demonstrated with poly and TaN electrodes, showing excellent subthreshold and drive current characteristics. The effects of NH3 pre-treatment on the electrical and reliability characteristics were also investigated. While thermal stability, EOT, leakage and breakdown were improved significantly, threshold voltage shifts, high hysteresis, poor MOSFET and poor reliability characteristics were obtained for the NH 3 pre-treated samples. In conclusion, promising electrical and material characteristics were obtained for Hf-silicates indicating that they are attractive candidates for alternative gate dielectric applications.

Gopalan, Sundararaman

210

Dielectric properties of dysprosium- and scandium-doped hafnium dioxide thin films  

NASA Astrophysics Data System (ADS)

Dysprosium- and scandium-doped HfO2 films have been deposited by atomic-vapor deposition on SiO2/Si substrates. Glancing-incidence x-ray diffraction demonstrates that Dy0.10Hf0.90Ox and Sc0.10Hf0.90Ox films show a cubic crystal structure, whereas HfO2 films are monoclinic. The dielectric permittivity increases strongly from 16 for HfO2 to 32 for Dy0.10Hf0.90Ox and Sc0.10Hf0.90Ox. This leads to a reduction of the leakage current in the tunneling regime by up to three orders of magnitude for constant effective oxide thickness. For thick films (>~6 nm), it is shown that leakage occurs via the Poole-Frenkel mechanism and that doping HfO2 increases leakage for constant physical oxide thickness.

Adelmann, C.; Sriramkumar, V.; van Elshocht, S.; Lehnen, P.; Conard, T.; de Gendt, S.

2007-10-01

211

Reliability of Strained SiGe Channel p-Channel MetalOxideSemiconductor Field-Effect Transistors with Ultra-Thin (EOT=3.1 nm) N2O-Annealed SiN Gate Dielectric  

Microsoft Academic Search

The p-channel metal-oxide-semiconductor field-effect transistor (pMOSFET) with 50-nm-thick Si0.85Ge0.15 channel and ultra-thin (EOT=3.1 nm) N2O-annealed SiN gate dielectric has been shown to have well-performing on\\/off and output characteristics. Several methodologies for the device reliability characterization, such as stress-induced-leakage-current (SILC), drain-avalanche-hot-carrier (DAHC) injection, channel hot-carrier (CHC) injection and negative-bias-temperature-instability (NBTI), have been used and the results were compared. In terms of

Ching-Wei Chen; Chao-Hsin Chien; Yi-Cheng Chen; Shih-Lu Hsu; Chun-Yen Chang

2005-01-01

212

Strong amplification of an electric field and electro-optical response in ultrathin heterostructures ferroelectric-linear dielectric  

NASA Astrophysics Data System (ADS)

An electroded heterostructure consisting of a dye layer sandwiched between two polymer ferroelectric layers is discussed. The dye layer plays a role of the probe of the electric field measured by an electroabsorption technique. Using this new method the electric field in ferroelectric and dielectric layers can be measured separately. When an a.c. voltage is applied to the heterostructure, the electric field in the dye layer increases 2.2 times (up to 0.55 GV/m), whereas the field in the ferroelectric decreases 2 times with respect to the average field in the entire structure. Moreover, the dye layer sandwiched between the ferroelectric layers may stand without breakdown the fields 5-7 times higher than a neat reference dye layer confined between metal electrodes. Therefore, the performance of electro-optical, electromechanical and other field controlled devices may be improved considerably when their functional materials are placed between ferroelectrics layers.

Blinov, L. M.; Lazarev, V. V.; Yudin, S. G.; Palto, S. P.

2012-04-01

213

Multicomponent dielectrics for oxide TFT  

NASA Astrophysics Data System (ADS)

In this work we present sputtered multicomponent dielectrics based on mixtures of HfO2 and SiO2. This way it is possible to get stable amorphous structure up to 800ºC, that does not happen for pure HfO2, for instance, that present a polycrystalline structure when deposited without any intentional substrate heating. Besides, also the band gap of the resulting films is increased when compared with pure HfO2 that theoretically is an advantage in getting a suitable band offset with the semiconductor layer on oxide TFTs. Concerning the electrical characterization, the leakage current on c-Si MIS structures is low as 10-9 Acm-2 at 10 V. The amorphous structure of the films also lead to better dielectric/semiconductor interfaces, as suggested by C-V characteristics on GIZO MIS structures, which do not present strong variation with frequency. On other hand, the dielectric constant decreases due to the incorporation of SiO2 and Al2O3. Further improvement on insulating and interface characteristics is achieved using multilayer stacks and substrate bias during deposition.

Pereira, Luís; Barquinha, Pedro; Gonçalves, Gonçalo; Fortunato, Elvira; Martins, Rodrigo

2012-02-01

214

Gas-phase reaction studies of dipositive hafnium and hafnium oxide ions: generation of the peroxide HfO2(2+).  

PubMed

Fourier transform ion cyclotron resonance mass spectrometry was used to characterize the gas-phase reactivity of Hf dipositive ions, Hf(2+)and HfO(2+), toward several oxidants: thermodynamically facile O-atom donor N(2)O, ineffective donor CO, and intermediate donors O(2), CO(2), NO, and CH(2)O. The Hf(2+) ion exhibited electron transfer with N(2)O, O(2), NO, and CH(2)O, reflecting the high ionization energy of Hf(+). The HfO(2+) ion was produced by O-atom transfer to Hf(2+) from N(2)O, O(2), and CO(2), and the HfO(2)(2+) ion by O-atom transfer to HfO(2+) from N(2)O; these reactions were fairly efficient. Density functional theory revealed the structure of HfO(2)(2+) as a peroxide. The HfO(2)(2+) ion reacted by electron transfer with N(2)O, CO(2), and CO to give HfO(2)(+). Estimates were made for the second ionization energies of Hf (14.5 ± 0.5 eV), HfO (14.3 ± 0.5 eV), and HfO(2) (16.2 ± 0.5 eV), and also for the bond dissociation energies, D[Hf(2+)-O] = 686 ± 69 kJ mol(-1) and D[OHf(2+)-O] = 186 ± 98 kJ mol(-1). The computed bond dissociation energies, 751 and 270 kJ mol(-1), respectively, are within these experimental ranges. Additionally, it was found that HfO(2)(2+) oxidized CO to CO(2) and is thus a catalyst in the oxidation of CO by N(2)O and that Hf(2+) activates methane to produce a carbene, HfCH(2)(2+). PMID:23186013

Lourenço, Célia; Michelini, Maria del Carmen; Marçalo, Joaquim; Gibson, John K; Oliveira, Maria Conceição

2012-12-27

215

Stabilization of higher-? tetragonal HfO2 by SiO2 admixture enabling thermally stable metal-insulator-metal capacitors  

NASA Astrophysics Data System (ADS)

The authors report the relationship between HfO2 crystalline phase and the resulting electrical properties. Crystallization of amorphous HfO2 into the monoclinic phase led to a significant increase in leakage current and formation of local defects. Admixture of 10% SiO2 avoided formation of these defects by stabilization of the tetragonal phase, and concurrently increased the permittivity to 35. This understanding enabled fabrication of crystalline HfO2 based metal-insulator-metal capacitors able to withstand a thermal budget of 1000 °C while optimizing capacitance equivalent thickness (<1.3 nm) at low leakage [J(1 V)<10-7 A/cm2].

Böscke, T. S.; Govindarajan, S.; Kirsch, P. D.; Hung, P. Y.; Krug, C.; Lee, B. H.; Heitmann, J.; Schröder, U.; Pant, G.; Gnade, B. E.; Krautschneider, W. H.

2007-08-01

216

Atomic-level imaging and properties of stray Hf atoms in Si-SiO2-HfO2 nanoscale structures.  

NASA Astrophysics Data System (ADS)

The aberration-corrected scanning transmission electron microscope (STEM) provides a new level of sensitivity for analyzing nanoscale oxide films. The sub-ångstrom probe provides much improved resolution, but equally important, greatly increased sensitivity to individual atoms. Single Hf atoms are visible within the nanometer thick SiO2 interlayer between a HfO2 dielectric and the Si substrate. Furthermore, the depth of focus of the aberration-corrected STEM is greatly reduced, and Hf atoms can be located in depth to better than 1 nm precision. Strikingly, no Hf atoms are seen to be in contact with the Si substrate, and exhibit preferred distances from the interface. First-principles density-functional calculations find that the energy of single Hf atoms rises sharply if they approach closer than ˜0.3 nm, in agreement with observations. The Hf atoms introduce localized states within the Si band gap, which are detected by electron energy loss spectroscopy. These states may mediate leakage currents. The effect of the stray Hf atoms on the electron mobility in the Si channel has been calculated using a novel first-principles approach and found to be consistent with measured mobility values. Work performed in collaboration with K. van Benthem, S. N. Rashkeev, M. H. Evans, and S. T. Pantelides.

Pennycook, Stephen

2006-03-01

217

Achieving 1 nm capacitive effective thickness in atomic layer deposited HfO2 on In0.53Ga0.47As  

NASA Astrophysics Data System (ADS)

A capacitive effective thickness (CET) value of 1.0 nm has been achieved in atomic layer deposited (ALD) high ? dielectrics HfO2 on In0.53Ga0.47As/InP. The key is a short air exposure under 10 min between removal of the freshly grown semiconductor epilayers and loading to the ALD reactor. This has led to minimal formation of the interfacial layer thickness, as confirmed using x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. The measured electrical characteristics of metal-oxide-semiconductor diodes of Au/Ti/HfO2(4.5 nm)/In0.53Ga0.47As showed a low leakage current density of 3.8×10-4 A/cm2 at VFB+1 V, which is about eight orders of magnitudes lower than that of SiO2 with the same CET. The capacitance-voltage curves show an overall ? value of 17-18, a nearly zero flatband shift, and an interfacial density of states Dit of 2×1012 cm-2 eV-1.

Lee, K. Y.; Lee, Y. J.; Chang, P.; Huang, M. L.; Chang, Y. C.; Hong, M.; Kwo, J.

2008-06-01

218

Oxygen Self-Diffusion in HfO_{2} Studied by Electron Spectroscopy.  

PubMed

High-resolution measurement of the energy of electrons backscattered from oxygen atoms makes it possible to distinguish between ^{18}O and ^{16}O isotopes as the energy of elastically scattered electrons depends on the mass of the scattering atom. Here we show that this approach is suitable for measuring oxygen self-diffusion in HfO_{2} using a Hf^{16}O_{2}(20??nm)/Hf^{18}O_{2} bilayers (60 nm). The mean depth probed (for which the total path length equals the inelastic mean free path) is either 5 or 15 nm in our experiment, depending on the geometry used. Before annealing, the elastic peak from O is thus mainly due to electrons scattered from ^{16}O in the outer layer, while after annealing the signal from ^{18}O increases due to diffusion from the underlying Hf^{18}O_{2} layer. For high annealing temperatures the observed interdiffusion is consistent with an activation energy of 1 eV, but at lower temperatures interdiffusion decreases with increasing annealing time. We interpret this to be a consequence of defects, present in the layers early on and enhancing the oxygen diffusivity, disappearing during the annealing process. PMID:24836258

Vos, M; Grande, P L; Venkatachalam, D K; Nandi, S K; Elliman, R G

2014-05-01

219

Oxygen Self-Diffusion in HfO2 Studied by Electron Spectroscopy  

NASA Astrophysics Data System (ADS)

High-resolution measurement of the energy of electrons backscattered from oxygen atoms makes it possible to distinguish between O18 and O16 isotopes as the energy of elastically scattered electrons depends on the mass of the scattering atom. Here we show that this approach is suitable for measuring oxygen self-diffusion in HfO2 using a HfO162(20nm)/HfO182 bilayers (60 nm). The mean depth probed (for which the total path length equals the inelastic mean free path) is either 5 or 15 nm in our experiment, depending on the geometry used. Before annealing, the elastic peak from O is thus mainly due to electrons scattered from O16 in the outer layer, while after annealing the signal from O18 increases due to diffusion from the underlying HfO182 layer. For high annealing temperatures the observed interdiffusion is consistent with an activation energy of 1 eV, but at lower temperatures interdiffusion decreases with increasing annealing time. We interpret this to be a consequence of defects, present in the layers early on and enhancing the oxygen diffusivity, disappearing during the annealing process.

Vos, M.; Grande, P. L.; Venkatachalam, D. K.; Nandi, S. K.; Elliman, R. G.

2014-05-01

220

Optical constants of crystalline HfO2 for energy range 140-930 eV  

SciTech Connect

We calculated the optical constants of the monoclinic phase of a HfO2 film from reflection spectra measured using synchrotron radiation in the spectral region from 143 eV to 927 eV, which includes the HfN4,5{sup -}, HfN2,3{sup -}, and OK absorption edges. The calculations were carried out using the Kramers-Kronig relations. It could be shown that the relation R(E){approx}E{sup -4} can be used for extrapolation of the experimental reflection spectrum of HfO2 (and probably of other heavy elements) for energies such that {theta}/{theta}c>3.7.

Filatova, Elena; Sokolov, Andrey; Andre, Jean-Michel; Schaefers, Franz; Braun, Walter

2010-05-10

221

Interface states for HfO2/Si structure observed by x-ray photoelectron spectroscopy measurements under bias  

NASA Astrophysics Data System (ADS)

A 1.0 nm silicon nitride (SiN) layer can prevent reaction between HfO2 and Si completely. In this case, the interface state spectra obtained from x-ray photoelectron spectroscopy measurements under bias have two peaks above and below the midgap, attributable to Si dangling bonds interacting weakly with an atom in SiN, indicating a high atomic density of the SiN layer. When a HfO2 layer is deposited on a 1.0 nm SiO2 layer, the SiO2 thickness increases to 1.6 nm. For this structure, one interface state peak is present near the midgap, attributable to isolated Si dangling bonds, indicating a low atomic density.

Maida, Osamu; Fukayama, Ken-Ichi; Takahashi, Masao; Kobayashi, Hikaru; Kim, Young-Bae; Kim, Hyun-Chul; Choi, Duck-Kyun

2006-09-01

222

A study of some optical properties of hafnium dioxide (HfO2) thin films and their applications  

Microsoft Academic Search

By use of evaporation conditions adjusted for the deposition of hafnium dioxide (HfO2), a series of films ranging in thickness from 50 to 10000 nm was prepared by using an electron beam gun inside an evacuated coating chamber of pressure 1×10-5 mbar. The films were obtained on optical glass substrate by using oxygen with a backfill pressure of 2.4×10-4 mbar

M. Fadel; O. A. Azim M; O. A. Omer; R. R. Basily

1998-01-01

223

Improvement of surface carrier mobility of HfO2 MOSFETs by high-temperature forming gas annealing  

Microsoft Academic Search

The surface electron mobility of HfO2 NMOSFETs with a polysilicon gate electrode was studied in terms of the effects of high-temperature forming gas (FG) annealing. The high-temperature FG annealing significantly improved the drive current or the surface electron mobility of the NMOSFETs. Improvements were also observed in the subthreshold swings and the C-V characteristics, indicating a reduction in interfacial state

Katsunori Onishi; Chang Seok Kang; Rino Choi; Hag-Ju Cho; Sundar Gopalan; Renee E. Nieh; Siddharth A. Krishnan; Jack C. Lee

2003-01-01

224

Self-ordered hexagonal nanoporous hafnium oxide and transition to aligned HfO2 nanotube layers  

Microsoft Academic Search

We show that hexagonally ordered HfO2 structures can either be grown to form a self-ordered pore or tube array, depending only on the electrochemical conditions during anodization of Hf in fluoride containing electrolytes. The water content in the electrolyte is the main factor affecting the transition from pores to tubes and the regularity of the structures. In the self-ordered nanoporous

Steffen Berger; Florian Jakubka; Patrik Schmuki

2009-01-01

225

Complete prevention of reaction at HfO 2/Si interfaces by 1 nm silicon nitride layer  

NASA Astrophysics Data System (ADS)

When hafnium oxide (HfO 2) is directly deposited on Si by the RF sputtering method, Hf silicide is formed and post-deposition anneal (PDA) at 400 °C transforms Hf silicide to Si suboxide plus Hf suboxide. The leakage current density for the diodes without PDA is high due to the high density interface states near the Fermi level (0.86 eV above the Si valence band maximum, VBM) and minute conduction channels. PDA at 400 °C eliminates the interface states and the conduction channels, and improves the characteristics of the HfO 2 layer, but interface states are newly formed at 0.53 eV above the VBM, resulting in still high leakage current density. Silicon nitride (SiN) layers formed by Si nitridation using N 2-plasma generated by the low energy electron impact method possess a high nitrogen atomic concentration ratio, N/(N + O) of 0.65. When a 1.0 nm SiN layer is inserted between HfO 2 and Si, interfacial reaction is completely prevented, resulting in a smaller effective oxide thickness, EOT of 1.4 nm. In spite of the smaller EOT, the leakage current density is nearly the same as that with no SiN layer, possibly due to the prevention of the formation of the conduction channels. PDA at 400 °C improves HfO 2 characteristics without causing the interfacial reaction, leading to a decrease in the leakage current density.

Kobayashi, Hikaru; Imamura, Kentaro; Fukayama, Ken-ichi; Im, Sung-Soon; Maida, Osamu; Kim, Young-Bae; Kim, Hyun-Chul; Choi, Duck-Kyun

2008-06-01

226

Low-temperature Polymorphs of ZrO2 and HfO2. A Density Functional Theory Study  

SciTech Connect

We present density functional calculations of the total energies and equations of state of the monoclinic, tetragonal, cubic, orthorhombic-I (Pbca) and orthorhombic-II (cotunnite)-structure phases of zirconia and hafnia in the local density (LDA) and generalized-gradient (GGA) approximations. The accuracy of the LDA approximation is not sufficient and GGA corrections are critical to obtain low-temperature phase transitions under pressure that are consistent with experiment, i.e., (monoclinic‡ orthorhombic-I ‡ cotunnite). The GGA values of the bulk modulus of the cotunnite phase were found to be 251 and 259 GPa for ZrO2 and HfO2, respectively. We developed a new population analysis scheme in which atomic radii are adapted to the actual charge distribution in the material. The results indicate that the effective atomic radius of Hf is smaller than that of Zr, which is a drastic manifestation of the relativistic lanthanide contraction. The population analysis results demonstrate that ionicity: (i) increases from the monoclinic to the cotunnite phase, and (ii) is larger for HfO2 than for ZrO2. This variable ionicity may be the reason why LDA fails to describe the relative stability of different polymorphs. The bandgap and heat of formation are also larger for monoclinic HfO2 than for ZrO2 by 0.6 eV and 0.60 eV/formula unit, respectively. The tetragonal phase, which often exists as a metastable phase at ambient conditions, has a bandgap larger than the monoclinic phase by 0.35 and 0.65 eV for ZrO2 and HfO2, respectively.

Jaffe, John E.; Bachorz, Rafal A.; Gutowski, Maciej S.

2005-10-20

227

Feature Modeling of HfO2 Atomic Layer Deposition Using HfCl4/H2O  

NASA Astrophysics Data System (ADS)

A Monte Carlo based feature scale model (Papaya) has been applied to atomic layer deposition (ALD) of HfO2 using HfCl_4/H_20. The model includes physical effects of transport to surface, specular and diffusive reflection within feature, adsorption, surface diffusion, deposition and etching. Discussed will be the 3D feature modeling of HfO2 deposition in assorted features (vias and trenches). The effect of feature aspect ratios, pulse times, cycle number, and temperature on film thickness, feature coverage, and film Cl fraction (surface/bulk) will be discussed. Differences between HfO2 ALD on blanket wafers and in features will be highlighted. For instance, the minimum pulse times sufficient for surface reaction saturation on blanket wafers needs to be increased when depositing on features. Also, HCl products created during the HfCl4 and H_20 pulses are more likely to react within a feature than at the field, reducing OH coverage within the feature (vs blanket wafer) thus limiting the maximum coverage attainable for a pulse over a feature.

Stout, Phillip J.; Adams, Vance; Ventzek, Peter L. G.

2003-03-01

228

Ion-radical synergy in HfO2 etching studied with a XeF2/Ar+ beam setup  

NASA Astrophysics Data System (ADS)

To gain more insight into fundamental aspects of the etching behavior of Hf-based high-k materials in plasma etch reactors, HfO2 films were etched in a multiple-beam setup consisting of a low energy Ar+ ion beam and a XeF2 radical beam. The etch rate and etch products were monitored by real-time ellipsometry and mass spectrometry, respectively. Although etching of HfO2 in XeF2/Ar+ chemistry is mainly a physical effect, an unambiguous proof of the ion-radical synergistic effect for the etching of HfO2 is presented. The etch yield for 400 eV Ar+ ions at a substrate temperature of 300 °C was 0.3 atoms/ion for Ar+ sputtering and increased to 2 atoms/ion when XeF2 was also supplied. The etch yield proved to follow the common square root of ion energy dependence both for pure sputtering and radical enhanced etching, with a threshold energy at room temperature of 69+/-17 eV for Ar+ ions and 54+/-14 eV for Ar+ ions with XeF2.

Gevers, P. M.; Beijerinck, H. C. W.; van de Sanden, M. C. M.; Kessels, W. M. M.

2008-04-01

229

Electrical and physico-chemical characterization of HfO 2\\/SiO 2 gate oxide stacks prepared by atomic layer deposition  

Microsoft Academic Search

In this paper, we have correlated electrical measurements of thin HfO2 layers deposited on SiO2 by atomic layer deposition with angle-resolved X-ray photoelectron spectroscopy experiments. Results show that the HfO2\\/Si interface layer (IL) is made of a SiOx layer underneath a Si-rich Hf-silicate layer. The increasing of the IL thickness, during annealing, was essentially due to the silicon oxidation by

J.-F. Damlencourt; O. Renault; D. Samour; A.-M. Papon; C. Leroux; F. Martin; S. Marthon; M.-N. Séméria; X. Garros

2003-01-01

230

GeOx interface layer reduction upon Al-gate deposition on a HfO2/GeOx/Ge(001) stack  

NASA Astrophysics Data System (ADS)

The metallization of HfO2/Ge by Al at room temperature was studied using photoemission and inverse photoemission. Upon deposition, Al reduces the GeOx interfacial layer between Ge and HfO2, and a thin Al2O3 layer is formed at the Al/HfO2 interface. The band alignment across the Al/HfO2/Ge stacks is also addressed.

Rangan, Sylvie; Bersch, Eric; Bartynski, Robert Allen; Garfunkel, Eric; Vescovo, Elio

2008-04-01

231

SnO2 Anode Surface Passivation by Atomic Layer Deposited HfO2 Improves Li-Ion Battery Performance.  

PubMed

For the first time, it is demonstrated that nanoscale HfO2 surface passivation layers formed by atomic layer deposition (ALD) significantly improve the performance of Li ion batteries with SnO2 -based anodes. Specifically, the measured battery capacity at a current density of 150 mAg(-1) after 100 cycles is 548 and 853 mAhg(-1) for the uncoated and HfO2 -coated anodes, respectively. Material analysis reveals that the HfO2 layers are amorphous in nature and conformably coat the SnO2 -based anodes. In addition, the analysis reveals that ALD HfO2 not only protects the SnO2 -based anodes from irreversible reactions with the electrolyte and buffers its volume change, but also chemically interacts with the SnO2 anodes to increase battery capacity, despite the fact that HfO2 is itself electrochemically inactive. The amorphous nature of HfO2 is an important factor in explaining its behavior, as it still allows sufficient Li diffusion for an efficient anode lithiation/delithiation process to occur, leading to higher battery capacity. PMID:24634208

Yesibolati, Nulati; Shahid, Muhammad; Chen, Wei; Hedhili, M N; Reuter, M C; Ross, F M; Alshareef, H N

2014-07-01

232

Diffusion and interface growth in hafnium oxide and silicate ultrathin films on Si(001)  

Microsoft Academic Search

Medium energy ion scattering has been used in combination with O16 and O18 isotope tracing to determine elemental depth distributions and elucidate oxygen transport in 2-5 nm thick HfO2 and HfSiOx films grown by atomic layer deposition on Si(001). Both the oxygen isotope exchange rate in the dielectric as well as the interfacial silicon oxide growth rates were examined as

L. V. Goncharova; M. Dalponte; T. Feng; T. Gustafsson; E. Garfunkel; P. S. Lysaght; G. Bersuker

2011-01-01

233

Charge storage characteristics of Au nanocrystal memory improved by the oxygen vacancy-reduced HfO2 blocking layer  

PubMed Central

This study characterizes the charge storage characteristics of metal/HfO2/Au nanocrystals (NCs)/SiO2/Si and significantly improves memory performance and retention time by annealing the HfO2 blocking layer in O2 ambient at 400°C. Experimental evidence shows that the underlying mechanism can be effectively applied to reduce oxygen vacancy and suppress unwanted electron trap-assisted tunneling. A memory window of 1 V at an applied sweeping voltage of ±2 V is also shown. The low program/erase voltage (±2 V) and the promising retention performances indicate the potential application of NCs in low-voltage, non-volatile memory devices.

2013-01-01

234

Charge storage characteristics of Au nanocrystal memory improved by the oxygen vacancy-reduced HfO2 blocking layer  

NASA Astrophysics Data System (ADS)

This study characterizes the charge storage characteristics of metal/HfO2/Au nanocrystals (NCs)/SiO2/Si and significantly improves memory performance and retention time by annealing the HfO2 blocking layer in O2 ambient at 400°C. Experimental evidence shows that the underlying mechanism can be effectively applied to reduce oxygen vacancy and suppress unwanted electron trap-assisted tunneling. A memory window of 1 V at an applied sweeping voltage of ±2 V is also shown. The low program/erase voltage (±2 V) and the promising retention performances indicate the potential application of NCs in low-voltage, non-volatile memory devices.

Tang, Ruifan; Huang, Kai; Lai, Hongkai; Li, Cheng; Wu, Zhiming; Kang, Junyong

2013-08-01

235

Physical properties and band structure of reactive molecular beam epitaxy grown oxygen engineered HfO2+/-x  

NASA Astrophysics Data System (ADS)

We have conducted a detailed thin film growth structure of oxygen engineered monoclinic HfO2+/-x grown by reactive molecular beam epitaxy. The oxidation conditions induce a switching between (111) and (002) texture of hafnium oxide. The band gap of oxygen deficient hafnia decreases with increasing amount of oxygen vacancies by more than 1 eV. For high oxygen vacancy concentrations, defect bands form inside the band gap that induce optical transitions and p-type conductivity. The resistivity changes by several orders of magnitude as a function of oxidation conditions. Oxygen vacancies do not give rise to ferromagnetic behavior.

Hildebrandt, Erwin; Kurian, Jose; Alff, Lambert

2012-12-01

236

Role of high-frequency power in C4F8 dual-frequency capacitively coupled plasmas treating high-k HfO2 films  

NASA Astrophysics Data System (ADS)

Plasma treatment of HfO2 films by octafluorocyclobutane (C4F8) 60 MHz(HF)/2 MHz(LF) dual-frequency capacitively coupled plasmas (DF-CCPs) was investigated. It is found that the fluorine atoms were incorporated into the HfO2 films by C4F8 DF-CCP treatment, but the C?:?F films were formed on the surface of the HfO2/Si gate stacks. The results also show that both the plasma treatment and the process of post-deposition annealing play major roles in stabilizing the tetragonal structure, leading to a large band gap and good electrical properties. The formation of t-HfO2 is related to oxygen vacancy generation and Si diffusion into the HfO2 films. The capacitance-voltage measurement showed that the smallest ?Vfb and the lowest interface trap density were obtained at the HF power of 120 W and the LF power of 30 W. Therefore, the C4F8 DF-CCP is a suitable method to improve the electrical characteristics of HfO2/Si gate stacks.

Zhang, H. Y.; Yang, X. M.; Yu, T.; Jin, C. G.; Ye, C.; Zhuge, L. J.; Wu, X. M.

2013-10-01

237

Indium diffusion through high-k dielectrics in high-k/InP stacks  

NASA Astrophysics Data System (ADS)

Evidence of indium diffusion through high-k dielectric (Al2O3 and HfO2) films grown on InP (100) by atomic layer deposition is observed by angle resolved X-ray photoelectron spectroscopy and low energy ion scattering spectroscopy. The analysis establishes that In-out diffusion occurs and results in the formation of a POx rich interface.

Dong, H.; Cabrera, W.; Galatage, R. V.; Santosh KC; Brennan, B.; Qin, X.; McDonnell, S.; Zhernokletov, D.; Hinkle, C. L.; Cho, K.; Chabal, Y. J.; Wallace, R. M.

2013-08-01

238

Effect of H and Si impurities on device performance based on HfO2 gate oxide  

NASA Astrophysics Data System (ADS)

Based on first-principles theoretical calculations, we investigate the hydrogenation effect on the defect properties of oxygen vacancies (VO) in HfO2. A defect complex of VO and H behaves as a shallow donor, being in a positive charge state for a wide range of the Fermi levels, and this complex is very stable against its dissociation into VO and H. We suggest that the VO-H complex is responsible for the formation of positive fixed charges, which neutralize negative fixed charges during the post-annealing process of SiOx/HfO2 stack. We find that at p+poly-Si/HfO2 gates, Si interstitials can be incorporated from the electrode into the gate oxide with a charge transfer to the electrode. The resulting interface dipole raises the Fermi level of poly-Si toward the pinning level, causing high flat band voltage shifts. In O-rich grown HfO2 on Si substrates, the Si atoms substitute for the Hf sites, leading to the formation of Hf-silicate layers, while under O-poor conditions, they remain as interstitial defects, binding with the Hf atoms, and behave as a negative-U trap, which causes the threshold voltage instability.

Kang, Joongoo; Kim, Dae Yeon; Chang, K. J.

2007-04-01

239

High damage threshold HfO2/SiO2 multilayer mirrors deposited by novel remote plasma sputtering  

NASA Astrophysics Data System (ADS)

Sputtering deposition coatings offer significant advantages on electron beam (EB) deposition, including high packing density, environmental stability and extremely low losses. But the inherent high compressive stress affects its application in high power laser system. This paper describes the technical feasibility of high damage threshold laser mirrors deposited by a novel remote plasma sputtering technique. This technique is based on generating intensive plasma remotely from the target and then magnetically steering the plasma to the target to realize the full uniform sputtering. The pseudo-independence between target voltage and target current provides us very flexible parameters tuning, especially for the films stress control. Deposition conditions are optimized to yield fully oxidized and low compressive stress single layer HfO2 and SiO2. The high damage threshold of 43.8 J/cm2 for HfO2/SiO2 laser mirrors at 1064 nm is obtained. For the first time the remote plasma sputtering is successfully applied in depositing laser mirrors with high performance.

Xu, Ying; Chen, Nan; Bu, Yi-Kun

2011-11-01

240

Growth, microstructure and electrical properties of sputter-deposited hafnium oxide (HfO2) thin films grown using HfO2 ceramic target  

SciTech Connect

Hafnium oxide (HfO?) thin films have been made by radio-frequency (rf) magnetron-sputtering onto Si(100) substrates under varying growth temperature (Ts). HfO? ceramic target has been employed for sputtering while varying the Ts from room temperature to 500?C during deposition. The effect of Ts on the growth and microstructure of deposited HfO? films has been studied using grazing incidence x-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), and high-resolution scanning electron microscopy (HR-SEM) coupled with energy dispersive x-ray spectrometry (EDS). The results indicate that the effect of Ts is significant on the growth, surface and interface structure, morphology and chemical composition of the HfO? films. Structural characterization indicates that the HfO? films grown at Ts<200 ?C are amorphous while films grown at Ts>200 ?C are nanocrystalline. An amorphous-to-crystalline transition occurs at Ts=200 ?C. Nanocrystalline HfO? films crystallized in a monoclinic structure with a (-111) orientation. XPS measurements indicated the high surface-chemical quality and stoichiometric nature of the grown HfO? films. An interface layer (IL) formation occurs due to reaction at the HfO?-Si interface for HfO? films deposited at Ts>200 ?C. The thickness of IL increases with increasing Ts. XPS and EDS at the HfO?-Si cross-section indicate the IL is a (Hf, Si)-O compound. The electrical characterization using capacitance-voltage measurements indicate that the dielectric constant decreases from 25 to 16 with increasing Ts.

Aguirre, B.; Vemuri, R. S.; Zubia, David; Engelhard, Mark H.; Shutthanandan, V.; Kamala Bharathi, K.; Ramana, Chintalapalle V.

2011-01-01

241

Demonstrating 1 nm-oxide-equivalent-thickness HfO2/InSb structure with unpinning Fermi level and low gate leakage current density  

NASA Astrophysics Data System (ADS)

In this work, the band alignment, interface, and electrical characteristics of HfO2/InSb metal-oxide-semiconductor structure have been investigated. By using x-ray photoelectron spectroscopy analysis, the conduction band offset of 1.78 +/- 0.1 eV and valence band offset of 3.35 +/- 0.1 eV have been extracted. The transmission electron microscopy analysis has shown that HfO2 layer would be a good diffusion barrier for InSb. As a result, 1 nm equivalent-oxide-thickness in the 4 nm HfO2/InSb structure has been demonstrated with unpinning Fermi level and low leakage current of 10-4 A/cm-2. The Dit value of smaller than 1012 eV-1cm-2 has been obtained using conduction method.

Trinh, Hai-Dang; Lin, Yueh-Chin; Nguyen, Minh-Thuy; Nguyen, Hong-Quan; Duong, Quoc-Van; Luc, Quang-Ho; Wang, Shin-Yuan; Nguyen, Manh-Nghia; Yi Chang, Edward

2013-09-01

242

355nm absorption in HfO2 and SiO2 monolayers with embedded Hf nanoclusters studied using photothermal heterodyne imaging  

NASA Astrophysics Data System (ADS)

The role of the Hf nanoclusters as near-UV, nanosecond-pulse laser-damage initiators in HfO2 and SiO2-pair-based multilayer coatings remains speculative. In this work we use photothermal heterodyne imaging (PHI) to investigate absorption in HfO2 and SiO2 monolayers containing embedded nanometer-sized Hf clusters produced by backsidethrough- thin-film ablation. Hf cluster size and areal-density distributions were characterized using transmission electron microscopy. PHI measurements were taken for cluster-containing samples and for similarly prepared HfO2 and SiO2 film samples of the same thickness without clusters. These data allow us to evaluate a possible role in the damageprocess initiation of two hypothetical sources of the localized absorption—Hf clusters and high-density areas of electronic defects.

Papernov, S.; Shin, E.; Murray, T.; Schmid, A. W.; Oliver, J. B.

2012-11-01

243

Electrical characteristics and thermal stability of HfO2 metal-oxide-semiconductor capacitors fabricated on clean reconstructed GaSb surfaces  

NASA Astrophysics Data System (ADS)

HfO2/GaSb interfaces fabricated by high-vacuum HfO2 deposition on clean reconstructed GaSb surfaces were examined to explore a thermally stable GaSb metal-oxide-semiconductor structure with low interface-state density (Dit). Interface Sb-O bonds were electrically and thermally unstable, and post-metallization annealing at temperatures higher than 200 °C was required to stabilize the HfO2/GaSb interfaces. However, the annealing led to large Dit in the upper-half band gap. We propose that the decomposition products that are associated with elemental Sb atoms act as interface states, since a clear correlation between the Dit and the Sb coverage on the initial GaSb surfaces was observed.

Miyata, Noriyuki; Ohtake, Akihiro; Ichikawa, Masakazu; Mori, Takahiro; Yasuda, Tetsuji

2014-06-01

244

Enhancement of longitudinal magneto-optical Kerr effect in HfO2/Co/HfO2/Al/silicon thin films  

NASA Astrophysics Data System (ADS)

In this paper, the longitudinal magneto-optical Kerr effect (MOKE) properties of the quadrilayer structure HfO2/Co/HfO2/Al/silicon are investigated experimentally and theoretically. The cavity enhancement of HfO2 on the magneto-optical (MO) Kerr response of the quadrilayer has been confirmed. The giant longitudinal Kerr rotation of ?1.04° at wavelength of 570 nm is tested when the cap and intermediate HfO2 layer thicknesses are 15 nm and 30 nm, respectively. The longitudinal Kerr rotation reversal in the wavelength range (440–720 nm) is also observed. It is strongly suggested that the enhanced MOKE stems from the optical reflection and interference of the quadrilayer structure.

Zhang, Shaoyin; Gao, Jinlong; Xia, Wenbin; Chen, Leyi; Tang, Yanmei; Li, Daoyong; Tang, Shaolong; Du, Youwei

2014-06-01

245

Formation of hafnium-aluminum-oxide gate dielectric using single cocktail liquid source in MOCVD process  

Microsoft Academic Search

We demonstrate that a high quality metal organic chemical vapor deposition (MOCVD) HfAlxOy (hereafter HfAlO) dielectric film can successfully be deposited with a wide range of composition controllability between HfO2 and Al2O3 in HfAlO using a single cocktail liquid source HfAl(MMP)2(OiPr)5. A composition ratio between 45 to 90% of HfO2 in HfAlO is achieved by controlling deposition process parameters. The

Moon Sig Joo; Byung Jin Cho; Chia Ching Yeo; Daniel Siu Hung Chan; Sung Jin Whoang; S. Mathew; L. Kanta Bera; N. Balasubramanian; Dim-Lee Kwong

2003-01-01

246

Comparative study of Laser induce damage of HfO2/SiO2 and TiO2/SiO2 mirrors at 1064 nm.  

PubMed

A comparative study of laser induced damage of HfO2/SiO2 and TiO2/SiO2 mirrors at 1064 nm has been carried out. One TiO2/SiO2 mirror with absorption of 300 ppm and two HfO2/SiO2 mirrors with absorption of 40 and 4.5 ppm were fabricated using electron beam evaporation method. For r-on-1 test, all HfO2/SiO2 mirrors with low average absorption are above 150 J/cm2 at 10 ns. However, the TiO2/SiO2 mirrors with high average absorption are just 9.5 J/cm2, which are probably due to the rather high absorption and rather low band gap energy. Meanwhile, all the samples were irradiated from front and back side respectively using the raster scan test mode. In case of front side irradiation, it is found that: for TiO2/SiO2 high reflectors, the representative damage morphologies are shallow pits that were probably caused by absorbing centers. However, for HfO2/SiO2 high reflectors, the dominant damage morphologies are micrometer-sized nodules ejected pits and the delamination initiating from the pits. The absorption of HfO2/SiO2 coatings is low enough to have minor influence on the laser damage resistance. In case of backside irradiation, the morphology of TiO2/SiO2 mirrors is mainly center melted pits that are thermal melting induced damage. Meanwhile, HfO2/SiO2 mirrors with isometrical fracture rings damage morphology are thermal induced stress damage. PMID:21369234

Jiao, Hongfei; Ding, Tao; Zhang, Qian

2011-02-28

247

Low Leakage Current Transport and High Breakdown Strength of Pulsed Laser Deposited HfO 2 \\/SiC Metal-Insulator-Semiconductor Device Structures  

Microsoft Academic Search

Hafnium oxide (HfO2) thin films were deposited by the pulsed laser deposition (PLD) method on SiC substrates. The bandgap of HfO2 thin films was observed to be 5.8 eV. The chemical nature and stoichiometry of the films were analyzed by x-ray photoelectron\\u000a spectroscopy (XPS). Metal-insulator-semiconductor (MIS) structures with Ni as a top electrode and TiN as a bottom electrode\\u000a were fabricated

S. S. Hullavarad; D. E. Pugel; E. B. Jones; R. D. Vispute; T. Venkatesan

2007-01-01

248

X-ray photoelectron spectroscopy of Er3+-activated SiO2-HfO2 glass-ceramic waveguides  

NASA Astrophysics Data System (ADS)

xHfO2-(100 - x) SiO2 (x = 10, 20, 30 mol%) glass-ceramic planar waveguides doped with 0.3 mol% Er3+ ions, prepared by the sol-gel route and heat treated at 1000 °C to nucleate HfO2 crystals, were analysed by x-ray photoelectron spectroscopy, x-ray diffraction, high resolution transmission electron microscopy and photoluminescence spectroscopy. Formation of tetragonal HfO2 nanocrystals has been evidenced in all the samples. Spectroscopic parameters concerning the 4I13/2 metastable state of Er3+ion are revisited as a function of XPS analysis.

Minati, L.; Speranza, G.; Micheli, V.; Ferrari, M.; Jestin, Y.

2009-01-01

249

Thermally stable ultra-thin nitrogen incorporated ZrO2 gate dielectric prepared by low temperature oxidation of ZrN  

Microsoft Academic Search

Ultra-thin nitrogen incorporated ZrO2 (ZrON) film is successfully prepared by low temperature oxidation of ZrN. Capacitance equivalent thickness (CET) of 15 Å with Jg=1 mA\\/cm2@ Vg=-1 V is demonstrated. There is no increase in CET up to 1000°C. Silicide formation at poly-Si\\/ZrO2\\/Si stack at high temperature annealing is also inhibited. In addition, the boron penetration from p+ poly-Si to Si

M. Koyama; K. Suguro; M. Yoshiki; Y. Kamimuta; M. Koike; M. Ohse; C. Hongo; A. Nishiyama

2001-01-01

250

O-vacancies in (i) nano-crystalline HfO2 and (i) non-crystalline SiO2 and Si3N4 studied by X-ray absorption spectroscopy.  

PubMed

Performance and reliability in semiconductor devices are limited by electronically active defects, primarily O-atom and N-atom vacancies. Synchrotron X-ray spectroscopy results, interpreted in the context of two-electron multiplet theories, have been used to analyze conduction band edge, and O-vacancy defect states in nano-crystalline transition metal oxides, e.g., HfO2, and the noncrystalline dielectrics, SiO2, Si3N4 and Si-oxynitride alloys. Two-electron multiplet theory been used to develop a high-spin state equivalent d2 model for O-vacancy allowed transitions and negative ion states as detected by X-ray absorption spectroscopy in the O K pre-edge regime. Comparisons between theory and experiment have used Tanabe-Sugano energy level diagrams for determining the symmetries and relative energies of intra-d-state transitions for an equivalent d2 ground state occupancy. Trap-assisted-tunneling, Poole-Frenkel hopping transport, and the negative bias temperature instability have been explained in terms of injection and/or trapping into O-atom and N-atom vacancy sites, and applied to gate dielectric, and metal-insulator-metal structures. PMID:22905534

Lucovsky, Gerald; Miotti, Leonardo; Bastos, Karen Paz

2012-06-01

251

Ion beam studies of Hafnium based alternate high-k dielectric films deposited on silicon  

NASA Astrophysics Data System (ADS)

Hafnium based high dielectric constant materials are critical for the state-of-the-art integrated circuit technology. As the size of the transistor decreases, the thickness of the gate dielectric (SiO2) should be reduced to maintain device capacitance at a desired level. This thickness reduction results in high OFF-state leakage current due to quantum tunneling. Recently alternate high-k materials, like HfO2, have been introduced as gate dielectrics. However deposition of these high-k materials on Si wafers results in high concentration of interface defects due to their thermodynamic instability on Si. Introduction of thin inter layer of Silicon oxide/nitrides between Si and HfO2 is expected to improve interface quality. Hence it is important to study the composition, thickness and intermixing effects to optimize the fabrication of Hafnium based Metal-Oxide-Semiconductor (MOS) devices. Here, we have performed High Resolution Rutherford Backscattering Spectrometry (HRBS) and X-ray Reflectivity (XRR) measurements to characterize HfO2/SiO2/Si samples. These samples were further irradiated by 80 MeV Ni ions to study ion induced inter-diffusion of Hf and Si across HfO2/Si interface as a function of ion fluence.

Manikanthababu, N.; Chan, T. K.; Pathak, A. P.; Devaraju, G.; Srinivasa Rao, N.; Yang, P.; Breese, M. B. H.; Osipowicz, T.; Nageswara Rao, S. V. S.

2014-08-01

252

Fabrication of BaTiO3-Based Dielectrics for Ultrathin-Layer Multilayer Ceramic Capacitor Application by a Modified Coating Approach  

NASA Astrophysics Data System (ADS)

The development of multilayer ceramic capacitor (MLCC) with base metal electrode (BME) requires precise controlling of the microstructure in a very thin dielectric layer (<1 ?m). In this paper, a modified coating approach for high coverage of BaTiO3 powder for further MLCC application has been developed. The well dispersed and coated BaTiO3 powders are prepared and the relative mechanism has been discussed. Furthermore, the ultrafine grained X7R dielectric ceramics were produced by both conventional mixing and modified coating methods. Compared with the conventional mixing method, the ceramics prepared by the coating approach exhibited better TCC (the temperature coefficient of capacitance) performance, with dielectric constant over 2000 and grain size below 150 nm. In addition, it is found through the coating method the content of additives can be reduced to a relatively smaller amount than that required in conventional mixing method.

Tian, Zhibin; Wang, Xiaohui; Zhang, Yichi; Song, Tae-Ho; Hur, Kang Heon; Li, Longtu

2011-02-01

253

Laser damage study of nodules in electron-beam-evaporated HfO2/SiO2 high reflectors.  

PubMed

A reactive electron beam evaporation process was used to fabricate 1.064??m HfO2/SiO2 high reflectors. The deposition process was optimized to reduce the nodular density. Cross-sectioning of nodular defects by a focused ion-beam milling instrument showed that the nodule seeds were the residual particles on the substrate and the particulates from the silica source "splitting." After optimizing the substrate preparation procedure and the evaporation process, a low nodular density of 2.7/mm2 was achieved. The laser damage test revealed that the ejection fluences and damage growth behaviors of nodules created from deep or shallow seeds were totally different. A mechanism based on directional plasma scald was proposed to interpret observed damage growth phenomenon. PMID:21460963

Cheng, Xinbin; Shen, Zhengxiang; Jiao, Hongfei; Zhang, Jinlong; Ma, Bin; Ding, Tao; Lu, Jiangtao; Wang, Xiaodong; Wang, Zhanshan

2011-03-20

254

Investigations of a New Diluted Magnetic Oxide with Room Temperature Ferromagnetism in Co-doped HfO2  

NASA Astrophysics Data System (ADS)

The structural, chemical, and magnetic properties of HfO2 epitaxial films ˜100nm thick grown on YSZ at varying growth temperature have been systematically investigated. Nearly cobalt cluster-free films with RT ferromagnetic behaviors can be obtained via low T growth. In-situ XPS analysis during growth indicated the formation of metallic cobalt at the initial growth stage under a low O2 partial pressure ˜10-10 Torr, and that the metallic cobalt can be mostly eliminated by raising the pressure to 10-7 Torr. In conjunction with EXAFS local structural analysis and post annealing experiments, we infer that cobalt ions in low T grown films are located at interstitial site and appeared to be stable after being annealed in O2 at 350^oC. Further Hall measurements are now underway to measure the carrier concentration, and to elucidate their role to the apparent ferromagnetism.

Chang, Y. H.; Lee, W. C.; Huang, M. L.; Lee, S. F.; Soo, Y. L.; Hong, M.; Kwo, J.

2007-03-01

255

Voltage and Power-Controlled Regimes in the Progressive Unipolar RESET Transition of HfO2-Based RRAM  

PubMed Central

Resistive switching (RS) based on the formation and rupture of conductive filament (CF) is promising in novel memory and logic device applications. Understanding the physics of RS and the nature of CF is of utmost importance to control the performance, variability and reliability of resistive switching memory (RRAM). Here, the RESET switching of HfO2-based RRAM was statistically investigated in terms of the CF conductance evolution. The RESET usually combines an abrupt conductance drop with a progressive phase ending with the complete CF rupture. RESET1 and RESET2 events, corresponding to the initial and final phase of RESET, are found to be controlled by the voltage and power in the CF, respectively. A Monte Carlo simulator based on the thermal dissolution model of unipolar RESET reproduces all of the experimental observations. The results contribute to an improved physics-based understanding on the switching mechanisms and provide additional support to the thermal dissolution model.

Long, Shibing; Perniola, Luca; Cagli, Carlo; Buckley, Julien; Lian, Xiaojuan; Miranda, Enrique; Pan, Feng; Liu, Ming; Sune, Jordi

2013-01-01

256

Ab initio study of the electrostatic dipole modulation due to cation substitution in HfO2/SiO2 interfaces  

NASA Astrophysics Data System (ADS)

The interface between HfO2 and SiO2 is of much technological interest for complementary metal-oxide semiconductor (CMOS) technology in microelectronic devices. The valence band offset between HfO2 and SiO2 is a property of particular importance for this interface because it can be modulated by adding substitutional cations like Al, La, and Mg. We study the effects of these substitutional cations within this interface by using ab initio techniques in order to obtain the electrostatic dipole modulation and the corresponding change in the valence band offset in relation to dopant free reference HfO2/SiO2 interfaces. Al, La, and Mg are substituted for both Hf and Si atoms close to the interface during a detailed analysis of the dipole at the microscopic scale. This reproduces not only the experimental trends, but also demonstrates that the effects of the dopants are strongly dependent upon their positions and their chemical environments. Specifically, the modulation of the charge distribution by the dopants shows a complicated structure consisting of several peaks that contribute to the interfacial dipole centered around the oxygen atoms that bridge between the HfO2 and the SiO2. We also include a first-order G0W0 correction to recover band offset results compatible with the experimental values.

Van Der Geest, A. G.; Blaise, P.; Richard, N.

2012-08-01

257

Physical and predictive models of ultrathin oxide reliability in CMOS devices and circuits  

Microsoft Academic Search

The microelectronics industry owes its considerable success largely to the existence of the thermal oxide of silicon. However, recently there is concern that the reliability of ultra-thin dielectrics will limit further scaling to slightly thinner than 2 mm. This paper will review the physics and statistics of dielectric wearout and breakdown in ultrathin SiO2-based gate dielectrics. Electrons or holes tunneling

James H. Stathis

2001-01-01

258

The electrical and material characterization of hafnium oxynitride gate dielectrics with TaN-gate electrode  

Microsoft Academic Search

Electrical and material characteristics of hafnium oxynitride (HfON) gate dielectrics have been studied in comparison with HfO2. HfON was prepared by a deposition of HfN followed by post-deposition-anneal (PDA). By secondary ion mass spectroscopy (SIMS), incorporated nitrogen in the HfON was found to pile up at the dielectric\\/Si interface layer. Based on the SIMS profile, the interfacial layer (IL) composition

Chang Seok Kang; Hag-Ju Cho; Rino Choi; Young-Hee Kim; Chang Yong Kang; Se Jong Rhee; Changhwan Choi; M. S. Akbar; J. C. Lee

2004-01-01

259

Tailoring the Interface Quality between HfO2 and GaAs via in Situ ZnO Passivation Using Atomic Layer Deposition.  

PubMed

We investigated ZnO surface passivation of a GaAs (100) substrate using an atomic layer deposition (ALD) process to prepare an ultrathin ZnO layer prior to ALD-HfO2 gate dielectric deposition. Significant suppression of both Ga-O bond formation near the interface and As segregation at the interface was achieved. In addition, this method effectively suppressed the trapping of carriers in oxide defects with energies near the valence band edge of GaAs. According to electrical analyses of the interface state response on p- and n-type GaAs substrates, the interface states in the bottom half of the GaAs band gap were largely removed. However, the interface trap response in the top half of the band gap increased somewhat for the ZnO-passivated surface. PMID:24911531

Byun, Young-Chul; Choi, Sungho; An, Youngseo; McIntyre, Paul C; Kim, Hyoungsub

2014-07-01

260

Dependence of Polarization and Dielectric response on Epitaxial Strain in (BaxSr1-x)TiO3 Ultrathin Films from First-Principles  

NASA Astrophysics Data System (ADS)

A first-principles-derived schemes is used to use a first-principles-derived technique to construct the temperature-versus-misfit strain phase diagrams for the whole BST composition rang (i.e., x=0.00,0.20,0.40,0.60,0.80,1.00). Moreover, we investigate the dependence of their dielectric and ferroelectric properties on the strain and the concentration. Our results reveal that the predicated phase diagrams show a topology similar to those calculated by Shirokov et. al. Phy. Rev. B. 79 144118 (2009) with quantitative discrepancies that will be revealed and explained. Our results also indicate that in-plane strain increases (respectively, decreases) the in-plane (respectively, out-of-plane) dielectric constants. Furthermore, the out-of-plane component of dielectric permittivity ?33 enhances with lowering x in (BaxSr1-x)TiO3 films. We hope that our results will be benefits to many scientists and will lead to new strategies for material design.

Bin-Omran, Saad

2012-02-01

261

Flexible and stretchable dielectrics  

Microsoft Academic Search

A brief tour d'horizon is given through recent research on flexible and stretchable dielectrics. Ultrathin dielectrics with low leakage currents and high breakdown strength are essential in flexible electronic devices, illustrated with low voltage field-effect transistors for optothermal sensing and flash memories. Electrets with a permanently stored electrical charge are useful to control the threshold voltage in field-effect devices. Ferroelectrets

Siegfried Bauer

2010-01-01

262

Phonon-scattering effects in CNT-FETs with different dimensions and dielectric materials  

NASA Astrophysics Data System (ADS)

The impact of acoustic and optical phonon scattering on the performance of CNT-FETs is investigated using a full-quantum transport model within the NEGF formalism. Different gate lengths, dielectric materials and chiralities are considered. It is shown that the use of a high- ? dielectric lowers the off-current dominated by phonon-assisted band-to-band tunneling. The device scalability is demonstrated: with the oxide thickness fixed to 1.5 nm, good performance is obtained with 15 nm and 10 nm gate lengths with SiO 2 and HfO 2 gate dielectrics, respectively. The role of phonon scattering in CNT-FETs of different chiralities is investigated for the HfO 2 devices. A similar analysis has also been carried out for source/drain underlap geometries. The results confirm that the calculation of the off-currents and delay times is strongly influenced by phonon scattering.

Grassi, Roberto; Poli, Stefano; Reggiani, Susanna; Gnani, Elena; Gnudi, Antonio; Baccarani, Giorgio

2008-09-01

263

Chemical states and electronic structure of a HfO(-2) / Ge(001) interface  

SciTech Connect

We report the chemical bonding structure and valence band alignment at the HfO{sub 2}/Ge (001) interface by systematically probing various core level spectra as well as valence band spectra using soft x-rays at the Stanford Synchrotron Radiation Laboratory. We investigated the chemical bonding changes as a function of depth through the dielectric stack by taking a series of synchrotron photoemission spectra as we etched through the HfO{sub 2} film using a dilute HF-solution. We found that a very non-stoichiometric GeO{sub x} layer exists at the HfO{sub 2}/Ge interface. The valence band spectra near the Fermi level in each different film structure were carefully analyzed, and as a result, the valence band offset between Ge and GeO{sub x} was determined to be {Delta}E{sub v} (Ge-GeO{sub x}) = 2.2 {+-} 0.15 eV, and that between Ge and HfO{sub 2}, {Delta}E{sub v} (Ge-HfO{sub 2}) = 2.7 {+-} 0.15 eV.

Seo, Kang-ill; McIntyre, Paul C.; /Stanford U., Materials Sci. Dept.; Sun, Shiyu; Lee, Dong-Ick; Pianetta, Piero; /SLAC, SSRL; Saraswat, Krishna C.; /Stanford U., Elect. Eng. Dept.

2005-05-04

264

Investigation of electrical properties of HfO2 metal-insulator-metal (MIM) devices  

NASA Astrophysics Data System (ADS)

This paper is devoted to the study of the electrical properties of Au/HfO2/TiN metal-insulator-metal (MIM) capacitors in three distinctive modes: (1) alternative mode (C-f), (2) dynamic regime [thermally stimulated currents, TSCs I(T)] and (3) static mode [I(V)]. The electrical parameters are investigated for different temperatures. It is found that capacitance frequency C-f characteristic possesses a low-frequency dispersion that arises for high temperature (T > 300 °C). Accordingly, the loss factor exhibits a dielectric relaxation (with an activation energy E a ~ 1.13 eV) which is intrinsically related to the diffusion of oxygen vacancies. The relaxation mechanisms of electrical defects in a dynamic regime (TSCs) analysis show that defect related to the TSC peak observed at 148.5 °C (E a ~ 1 eV) is in agreement with impedance spectroscopy (C-f). On the other hand, when the MIM structures are analyzed in static mode, the I-V plots are governed by Schottky emission. The extrapolation of the curve at zero field gives a barrier height of 1.7 eV.

Khaldi, O.; Jomni, F.; Gonon, P.; Mannequin, C.; Yangui, B.

2014-02-01

265

High-performance self-aligned inversion-channel In0.53Ga0.47As metal-oxide-semiconductor field-effect-transistors by in-situ atomic-layer-deposited HfO2  

NASA Astrophysics Data System (ADS)

Self-aligned inversion-channel In0.53Ga0.47As metal-oxide-semiconductor field-effect-transistors (MOSFETs) have been fabricated using the gate dielectrics of in-situ directly atomic-layer-deposited (ALD) HfO2 followed by ALD-Al2O3. There were no surface pretreatments and no interfacial passivation/barrier layers prior to the ALD. TiN/Al2O3 (4 nm)/HfO2 (1 nm)/In0.53Ga0.47As/InP MOS capacitors exhibited well-behaved capacitance-voltage characteristics with true inversion behavior, low leakage current densities of ˜10-8 A/cm2 at ±1 MV/cm, and thermodynamic stability at high temperatures. Al2O3 (3 nm)/HfO2 (1 nm)/In0.53Ga0.47As MOSFETs of 1 ?m gate length, with 700 °C-800 °C rapid thermal annealing in source/drain activation, have exhibited high extrinsic drain current (ID) of 1.5 mA/?m, transconductance (Gm) of 0.84 mS/?m, ION/IOFF of ˜104, low sub-threshold swing of 103 mV/decade, and field-effect electron mobility of 1100 cm2/V · s. The devices have also achieved very high intrinsic ID and Gm of 2 mA/?m and 1.2 mS/?m, respectively.

Lin, T. D.; Chang, W. H.; Chu, R. L.; Chang, Y. C.; Chang, Y. H.; Lee, M. Y.; Hong, P. F.; Chen, Min-Cheng; Kwo, J.; Hong, M.

2013-12-01

266

Application of zero-temperature-gradient zero-bias thermally stimulated current spectroscopy to ultrathin high-dielectric-constant insulator film characterization  

NASA Astrophysics Data System (ADS)

Previously, we have reported our application of the zero-bias thermally stimulated current (ZBTSC) spectroscopy technique to study defect states in high-dielectric-constant insulator films such as tantalum oxide with much less parasitic current which can be a serious limitation for the conventional thermally stimulated current method. However, a parasitic current can still be observed for ZBTSC because of a small parasitic temperature gradient across the sample. The thermal design of the ZBTSC system can be improved, resulting in zero-temperature-gradient ZBTSC which can be used to detect deeper traps than those by ZBTSC.

Lau, W. S.; Wong, K. F.; Han, Taejoon; Sandler, Nathan P.

2006-04-01

267

H-shuttling within a Hf-defect complex in Si/SiO2/HfO2 structures  

NASA Astrophysics Data System (ADS)

It was recently shown that, following irradiation of Si-SiO2/HfO2 structures by X-rays or constant-voltage stress, both oxide- and interface-trap densities exhibit oscillations with switch-bias annealing that are much larger than those previously observed in Si/SiO2 devices. Here we describe a particular defect complex that can account for the observations. The complex comprises a suboxide Hf-Si bond and an interfacial dangling bond (Pb center). With the aid of first-principles calculations we show that this defect possesses a symmetric double-well minimum and can provide trapping sites for H atoms near the interface. In the first site, the H atom passivates the dangling bond; in the second site the H atom resides near the center of the Hf-Si bond. A moderate intervening barrier (1.2 eV) suggests a relatively easy hopping of H atoms between these two energy minima, aided by the applied field and temperature. This shuttling mechanism can explain the observed oscillations in the interface trap densities during switched-bias conditions. This work was supported in part by the AFOSR and the DOE.

Marinopoulos, A. G.; Batyrev, I.; Zhou, X.; Schrimpf, R.; Fleetwood, D.; Pantelides, S. T.

2008-03-01

268

Study of HfO2/SiO2 dichroic laser mirrors with refractive index inhomogeneity.  

PubMed

HfO2/SiO2 dichroic mirrors, having high reflectance at 1064 nm and high transmittance at 532 nm, play an important role in high-power laser systems. However, the half-wave hole effect, caused mainly by the refractive index inhomogeneity of hafnia, affects the spectra and application of these mirrors. Two approaches to eliminate the half-wave hole effect have been proposed. Both approaches attempt to shift the location of the half-wave hole in comparison with the original wavelength. One approach broadens the reflectance band of the first harmonic wavelength and simultaneously adjusts the central reflectance band to a longer wavelength, whereas the other approach combines the two stacks to adjust the location of the half-wave hole far away from the wavelength of interest. Two kinds of dichroic mirrors have been successfully fabricated; moreover, it was found that the method of a two-stack combination, 0.9(HL)8 and 1.1(HL)8, provides designs that can be fabricated more easily and with better quality spectral characteristics. PMID:24514250

Jiao, Hongfei; Cheng, Xinbin; Bao, Ganghua; Han, Jin; Zhang, Jinlong; Wang, Zhanshan; Trubetskov, M; Tikhonravov, Alexander V

2014-02-01

269

Addition of HfO2 interface layer for improved synaptic performance of phase change memory (PCM) devices  

NASA Astrophysics Data System (ADS)

In this work, we will focus on the use of phase change memory (PCM) to emulate synaptic behavior in emerging neuromorphic system-architectures. In particular, we will show that the performance and energy-efficiency of large scale neuromorphic systems can be improved by engineering individual PCM devices used as synapses. This is obtained by adding a thin HfO2 interface layer to standard GST PCM devices, allowing for the lowering of the Set/Reset currents and the increase of the number of intermediate resistance states (or synaptic weights) in the synaptic potentiation characteristics. The experimentally obtained potentiation characteristics of such PCM devices are used to simulate a 2-layer ultra-dense spiking neural network (SNN) and to perform a complex visual pattern extraction from a test case based on real world data (i.e. cars passing on a 6-lane freeway). The total power dissipated in the learning mode, for the pattern extraction experiment is estimated to be as low as 60 ?W. Average detection rate of cars is found to be greater than 90%.

Suri, M.; Bichler, O.; Hubert, Q.; Perniola, L.; Sousa, V.; Jahan, C.; Vuillaume, D.; Gamrat, C.; DeSalvo, B.

2013-01-01

270

Wide band antireflective coatings Al2O3 / HfO2 / MgF2 for UV region  

NASA Astrophysics Data System (ADS)

Deposition technology of the three layers antireflective coatings consists of hafnium compound are presented in this paper. Oxide films were deposited by means of e-gun evaporation in vacuum of 5x10-5 mbar in presence of oxygen and fluoride films by thermal evaporation. Substrate temperature was 250°C. Coatings were deposited onto optical lenses made from quartz glass (Corning HPFS). Thickness and deposition rate were controlled by thickness measuring system Inficon XTC/2. Simulations leading to optimization of thickness and experimental results of optical measurements carried during and after deposition process were presented. Physical thickness measurements were made during deposition process and were equal to 43 nm/74 nm/51 nm for Al2O3 / HfO2 / MgF2 respectively. Optimization was carried out for ultraviolet region from 230nm to the beginning of visible region 400 nm. In this region the average reflectance of the antireflective coating was less than 0.5% in the whole range of application.

Winkowski, P.; Marsza?ek, Konstanty W.

2013-07-01

271

In situ study of the role of substrate temperature during atomic layer deposition of HfO2 on InP  

NASA Astrophysics Data System (ADS)

The dependence of the ``self cleaning'' effect of the substrate oxides on substrate temperature during atomic layer deposition (ALD) of HfO2 on various chemically treated and native oxide InP (100) substrates is investigated using in situ X-ray photoelectron spectroscopy. The removal of In-oxide is found to be more efficient at higher ALD temperatures. The P oxidation states on native oxide and acid etched samples are seen to change, with the total P-oxide concentration remaining constant, after 10 cycles of ALD HfO2 at different temperatures. An (NH4)2 S treatment is seen to effectively remove native oxides and passivate the InP surfaces independent of substrate temperature studied (200 °C, 250 °C and 300 °C) before and after the ALD process. Density functional theory modeling provides insight into the mechanism of the changes in the P-oxide chemical states.

Dong, H.; Santosh, K. C.; Qin, X.; Brennan, B.; McDonnell, S.; Zhernokletov, D.; Hinkle, C. L.; Kim, J.; Cho, K.; Wallace, R. M.

2013-10-01

272

The combined study of Dy2O3-HfO2 nanocrystallites formation by means of EXAFS, PDF, XRD and SAXS  

NASA Astrophysics Data System (ADS)

The process of double oxide Dy2O3-HfO2 nanocrystallites formation upon annealing to 1600°C was investigated with the combination off few X-ray and synchrotron methods. XRD and PDF show the mean crystal structure to be fluorite typical for the compounds of Ln2O3-MeO2 type. The ordering of structure and the growth of nanocrystallites upon annealing was estimated independently from XRD patterns, PDF functions and SAXS scattering curves. Neither transition to pyrochlore phase, nor signs of recently shown in related Gd2O3-HfO2 compounds pyrochlore-type superstructure is observed. However, EXAFS and the short range order of PDF clearly indicate the discrepancy between Dy and Hf local environment. Such a disorder of local crystal structure cannot be described by the fluorite model.

Yaroslavtsev, A. A.; Menushenkov, A. P.; Leshchev, D. S.; Bednarcik, J.; Chernikov, R. V.; Zubavichus, Y. V.; Popov, V. V.; Petrunin, V. F.; Korovin, S. A.

2013-03-01

273

Band alignment and interfacial structure of ZnO/Si heterojunction with Al2O3 and HfO2 as interlayers  

NASA Astrophysics Data System (ADS)

Energy band alignment of ZnO/Si heterojunction with thin interlayers Al2O3 and HfO2 grown by atomic layer deposition has been studied using x-ray photoelectron spectroscopy. The valence band offsets of ZnO/Al2O3 and ZnO/HfO2 heterojunctions have been determined to be 0.43 and 0.22 eV, respectively. Accordingly, the band alignment ZnO/Si heterojunction is then modified to be 0.34 and 0.50 eV through inserting a thin Al2O3 and HfO2 layer, respectively. The feasibility to tune the band structure of ZnO/Si heterojunction by selecting a proper interlayer shows great advantage in improving the performance of the ZnO-based optoelectronic devices.

Lu, Hong-Liang; Yang, Ming; Xie, Zhang-Yi; Geng, Yang; Zhang, Yuan; Wang, Peng-Fei; Sun, Qing-Qing; Ding, Shi-Jin; Wei Zhang, David

2014-04-01

274

A higher-k tetragonal HfO2 formed by chlorine plasma treatment at interfacial layer for metal-oxide-semiconductor devices  

NASA Astrophysics Data System (ADS)

A tetragonal HfO2 (t-HfO2) with higher-k value and large band gap is investigated in this work. X-ray diffraction analysis shows a t-HfO2 can be formed by using Cl2 plasma treatment at the HfO2/Si interface after a post deposition annealing at 650 °C. The mechanisms of t-HfO2 formation can be attributed to the Si diffusion and oxygen vacancy generation which are formed by Cl2 plasma treatment. From the cross-sectional transmission electron microscope and capacitance-voltage measurement, the k value of this t-HfO2 is estimated to be about 35. The optical band gap value for t-HfO2 is similar to that of the monoclinic.

Fu, Chung-Hao; Chang-Liao, Kuei-Shu; Li, Chen-Chien; Ye, Zong-Hao; Hsu, Fang-Ming; Wang, Tien-Ko; Lee, Yao-Jen; Tsai, Ming-Jinn

2012-07-01

275

Band offsets of HfO2/GeON/Ge stacks measured by ultraviolet and soft x-ray photoelectron spectroscopies  

NASA Astrophysics Data System (ADS)

Electronic properties of the HfO2/GeON/Ge stacks were studied using ultraviolet and synchrotron radiation photoelectron spectroscopies. The valence band offset of HfO2 with Ge is equal to 2.9+/-0.1 eV. Intermediate electronic states were observed in the GeON band gap related to structural defects, oxygen vacancies, and N 2p states. As a consequence, the GeON valence band offset with Ge is reduced by 2.4+/-0.1 eV to reach 1.2+/-0.1 eV. This value is lower than the previous reported results with a GeOx interfacial layer, but still compatible with the semiconductor technology.

Martinez, E.; Renault, O.; Fourdrinier, L.; Clavelier, L.; Le Royer, C.; Licitra, C.; Veyron, T.; Hartmann, J. M.; Loup, V.; Vandroux, L.; Guittet, M. J.; Barrett, N.

2007-01-01

276

Al 2O 3\\/SiO 2 and HfO 2\\/SiO 2 dichroic mirrors for UV solid-state lasers  

Microsoft Academic Search

HfO2\\/SiO2 and Al2O3\\/SiO2 multilayers to be employed as high reflectance end mirrors in Cerium-doped fluoride solid-state lasers were produced by radio frequency sputtering. The components were designed to have high transmittance at the pumping wavelength and high reflectance in a wavelength band corresponding to the active medium emission. A photoacoustic beam deflection technique and inspection of the irradiated area under

Maria Luisa Grilli; Francesca Menchini; Angela Piegari; Daniele Alderighi; Guido Toci; Matteo Vannini

2009-01-01

277

SiO2/HfO2 multilayers: impact of process parameters and stack geometry on the optical and structural properties  

NASA Astrophysics Data System (ADS)

We present a complete systematic study on the effect of assist beam energy on SiO2/HfO2 quarter wave stacks deposited by dual ion beam sputter (DIBS) deposition. Increasing assist beam energy results in lower surface roughness and reduced micro-crystallinity. The coatings also show reduced mechanical stress. The improvements in the structural properties are accompanied by a reduction in the absorption loss and an increase in the laser resistance to damage at 1 ?m.

Patel, D.; Langston, P.; Markosyan, A.; Krous, E. M.; Langdon, B.; Furch, F.; Reagan, B.; Route, R.; Fejer, M. M.; Rocca, J. J.; Menoni, C. S.

2008-12-01

278

Characterization of Ultrathin Ta-oxide Films Formed on Ge(100) by ALD and Layer-by-Layer Methods  

NASA Astrophysics Data System (ADS)

Atomic layer deposition (ALD) and Layer-by-Layer deposition of Ta-oxide films on Ge(100) with using tris (tert-butoxy) (tert-butylimido) tantalum have been studied systematically. From the analysis of the chemical bonding features of the interface between TaOx and Ge(100) using x-ray photoelectron spectroscopy (XPS), Ge atom diffusion into the Ta oxide layer and resultant TaGexOy formation during deposition at temperatures higher than 200°C were confirmed. Also, we have demonstrated that nanometer-thick deposition of Tantalum oxide as an interfacial layer effectively suppresses the formation of GeOx in the HfO2 ALD on Ge. By the combination of TaOx pre-deposition on Ge(100) and subsequent ALD of HfO2, a capacitance equivalent thickness (CET) of 1.35 nm and relative dielectric constant of 23 were achieved.

Mishima, K.; Murakami, H.; Ohta, A.; Sahari, S. K.; Fujioka, T.; Higashi, S.; Miyazaki, S.

2013-03-01

279

Effect of current compliance and voltage sweep rate on the resistive switching of HfO2/ITO/Invar structure as measured by conductive atomic force microscopy  

NASA Astrophysics Data System (ADS)

The electrical characterization of HfO2/ITO/Invar resistive switching memory structure was studied using conductive atomic force microscopy (AFM) with a semiconductor parameter analyzer, Agilent 4156C. The metal alloy Invar was used as the metal substrate to ensure good ohmic contact with the substrate holder of the AFM. A conductive Pt/Ir AFM tip was placed in direct contact with the HfO2 surface, such that it acted as the top electrode. Nanoscale current-voltage (I-V) characteristics of the HfO2/ITO/Invar structure were measured by applying a ramp voltage through the conductive AFM tip at various current compliances and ramp voltage sweep rates. It was found that the resistance of the low resistance state (RLRS) decreased with increasing current compliance value, but resistance of high resistance state (RHRS) barely changed. However, both the RHRS and RLRS decreased as the voltage sweep rate increased. The reasons for this dependency on current compliance and voltage sweep rate are discussed.

Wu, You-Lin; Liao, Chun-Wei; Ling, Jing-Jenn

2014-06-01

280

Nanomechanical properties of sputter-deposited HfO2 and HfxSi1-xO2 thin films  

NASA Astrophysics Data System (ADS)

The mechanical properties of sputter-deposited HfO2 and HfxSi1-xO2 films were studied as a function of composition using nanoindentation. The elastic modulus and hardness were measured at room temperature for as-deposited films of varying Hf content and for films subjected to annealing at 1000 °C. The elastic modulus and hardness of as-deposited films were found to increase monotonically with increasing HfO2 content, with the hardness increasing from 5.0 +/- 0.3 GPa for pure SiO2 to 8.4 +/- 0.4 GPa for pure HfO2. All films were found to be harder after annealing at 1000 °C, with the increase for SiO2 films attributed to densification of the SiO2 network and that for the HfxSi1-xO2 films to a combination of phase separation, densification, and crystallization.

Venkatachalam, D. K.; Bradby, J. E.; Saleh, M. N.; Ruffell, S.; Elliman, R. G.

2011-08-01

281

Segregation trends of the metal alloys Mo-Re and Mo-Pt on HfO2: A first-principles study  

NASA Astrophysics Data System (ADS)

Using first-principles calculations, we compared the segregation trends at the surface of metal alloys with those at an interface with HfO2. The choice of this oxide was motivated by its significance as a potential replacement for SiO2 in advanced transistors. We considered Mo-Re and Mo-Pt alloys as typical examples of disordered and ordered alloys, respectively. The segregation to the surface/interface was analyzed in terms of metal and oxygen adsorption energies. It is shown that chemical bonding at the metal/oxide interface strongly influences segregation both in Mo-Re and Mo-Pt alloys. In particular, bonding with oxygen atoms at the oxide/Mo-Re alloy interface depletes the Re content of the interfacial layer. In the case of Mo-Pt on HfO2 an oxygen-rich interface promotes the formation of one monolayer (but not two monolayers) of Mo separating PtMox from HfO2, while a stoichiometric interface favors an abrupt PtMox/HfO2 interface. This study also shows that the presence of Mo in the alloy stabilizes Pt which can potentially decrease the tendency of Pt to diffuse into the oxide matrix. The individual constituents of these intermetallic compounds exhibit high vacuum work functions, and therefore these alloys are also likely to have sufficiently high work functions to be considered as promising candidates for p-type gate electrodes in future generations of transistors.

Knizhnik, A. A.; Gavrikov, A. V.; Safonov, A. A.; Iskandarova, I. M.; Bagatur'yants, A. A.; Potapkin, B. V.; Fonseca, L. R. C.; Stoker, M. W.

2006-07-01

282

Effects of the oxygen precursor on the electrical and structural properties of HfO2 films grown by atomic layer deposition on Ge  

NASA Astrophysics Data System (ADS)

We report on the growth by atomic layer deposition of HfO2 films on HF-last treated Ge(001) substrates using HfCl4 as a Hf source and either O3 or H2O as oxygen sources. The choice of the oxygen precursor strongly influences the structural, chemical, and electrical properties of the HfO2 films: Those grown using H2O exhibit local epitaxial growth, a large amount of contaminants such as chlorine and carbon, and a large frequency dispersion of the capacitance-voltage (C-V) characteristics. Films grown using O3 are good insulators and exhibit well-shaped C-V curves with a minimum frequency dispersion of the accumulation capacitance. Moreover, they are smoother, less crystallized, and with a lower contaminant content than those grown using H2O. However, the use of O3 leads to the formation of a 2 nm thick layer, possibly GeOx, at the HfO2/Ge interface.

Spiga, S.; Wiemer, C.; Tallarida, G.; Scarel, G.; Ferrari, S.; Seguini, G.; Fanciulli, M.

2005-09-01

283

Thermal conductivity and thermal cycle life of La 2O 3 and HfO 2 doped ZrO 2–Y 2O 3 coatings produced by EB-PVD  

Microsoft Academic Search

The effects of La2O3 and HfO2 addition on thermal conductivity and thermal cycle life of EB-PVD YSZ coatings were investigated. La2O3 and HfO2 were selected as additives, because they significantly suppress the sintering of YSZ. The developed coating showed low thermal conductivity as well as high resistance to sintering. Burner rig tests confirmed that the developed coating have a superior

Mineaki Matsumoto; Takeharu Kato; Norio Yamaguchi; Daisaku Yokoe; Hideaki Matsubara

2009-01-01

284

Electrical characterization of high K dielectrics and metals, modeling of dielectric response, and modification of metal work function  

NASA Astrophysics Data System (ADS)

During the deposition of HfO2 gate oxide by atomic layer deposition (ALD) and post deposition annealing, it is observed that SiOx growth on Si, interdiffusion of Hf, Si, and O species, formation of Hf-O-Si bond linkages and amorphous Hf silicates through reactions at internal interfaces, and nucleation and growth of HfO2 occurs. Due to this intermixing, an intermediate layer with graded composition and dielectric permittivity (K) is formed, and which must be taken into account to model the total equivalent oxide thickness (EOTtot) of the stack. Therefore, quantum corrected EOTtot of this stack was estimated from C-V measurements, and using a three-layer capacitance model, that reflects the spatial dependence of composition (and K) in the dielectric sub-layers, the respective contributions to EOT tot and the K of the interfacial layer are determined. Since the interlayer contribution to the EOTtot is about 50%, nitridation of the interface is carried out to reduce its effect. Additionally, ALD silicates are used to control the nanostructure evolution and thermal stability of the HfO 2 layer, for these Hf-Si-O films with various HfO2 content (40, 60, and 75 mol%) are electrically characterized. The properties of as-deposited and forming gas annealed (FGA) Ta 2O5 thin-film capacitors deposited by ALD and plasma-enhanced ALD (PEALD) on native oxide surface (SiOx/Si) are examined and qualitatively compared using cross-sectional high resolution transmission electron microscopy (HRTEM), high angle annular dark field scanning TEM (HAADF-STEM) equipped with parallel electron energy loss spectrometer (PEELS), capacitance-voltage (C-V) and leakage current-voltage (JL-V) techniques, and oxide breakdown statistics. The effective metal work function (?M,eff) for Ru, Re, Pt and Pd on ALD HfO2, which are different from the vacuum work function and important for device threshold voltage control, are measured by the C-V method, and the extracted charge neutrality level (? CNL,HK) and screening parameter (S) are correlated with the stoichiometry and permittivity of the HfO2 film. Finally, a novel method is used to change the ?Ti,eff using self-assembled monolayer (SAM) of dipolar molecules, aminopropyl triethoxy silane or APTES molecules; a chance attributed to the change in the electric potential at the Ti/SAM interface.

Gu, Diefeng

285

Impacts of Zr Composition in $\\\\hbox{Hf}_{1-x} \\\\hbox{Zr}_{x}\\\\hbox{O}_{y}$ Gate Dielectrics on Their Crystallization Behavior and Bias-Temperature-Instability Characteristics  

Microsoft Academic Search

The effects of Zr composition on the crystallization behaviors and reliability characteristics of atomic-layer-deposited Hf1?xZrxOy (0 ? x ? 1) gate-dielectric films are examined. n-Channel metal-oxide-semiconductor field-effect transistor (nMOSFET) devices with ZrO2 gate dielectrics showed a much smaller Vth shift under the positive bias stress compared with the same device with HfO 2 gate dielectrics. The impact of Zr composition

Hyung-Suk Jung; So-Ah Lee; Sang-ho Rha; Sang Young Lee; Hyo Kyeom Kim; Do Hyun Kim; Kyu Hwan Oh; Jung-Min Park; Weon-Hong Kim; Min-Woo Song; Nae-In Lee; Cheol Seong Hwang

2011-01-01

286

Ab initio localized basis set study of structural parameters and elastic properties of HfO2 polymorphs  

NASA Astrophysics Data System (ADS)

The SIESTA approach based on pseudopotentials and a localized basis set is used to calculate the electronic, elastic and equilibrium properties of P 21/c, Pbca, Pnma, Fm3m, P42nmc and Pa3 phases of HfO2. Using separable Troullier-Martins norm-conserving pseudopotentials which include partial core corrections for Hf, we tested important physical properties as a function of the basis set size, grid size and cut-off ratio of the pseudo-atomic orbitals (PAOs). We found that calculations in this oxide with the LDA approach and using a minimal basis set (simple zeta, SZ) improve calculated phase transition pressures with respect to the double-zeta basis set and LDA (DZ-LDA), and show similar accuracy to that determined with the PPPW and GGA approach. Still, the equilibrium volumes and structural properties calculated with SZ-LDA compare better with experiments than the GGA approach. The bandgaps and elastic and structural properties calculated with DZ-LDA are accurate in agreement with previous state of the art ab initio calculations and experimental evidence and cannot be improved with a polarized basis set. These calculated properties show low sensitivity to the PAO localization parameter range between 40 and 100 meV. However, this is not true for the relative energy, which improves upon decrease of the mentioned parameter. We found a non-linear behaviour in the lattice parameters with pressure in the P 21/c phase, showing a discontinuity of the derivative of the a lattice parameter with respect to external pressure, as found in experiments. The common enthalpy values calculated with the minimal basis set give pressure transitions of 3.3 and 10.8 GPa for P2_1/c \\rightarrow Pbca and Pbca \\rightarrow Pnma , respectively, in accordance with different high pressure experimental values.

Caravaca, M. A.; Casali, R. A.

2005-09-01

287

Femtosecond dynamics of dielectric films in the pre-ablation regime  

NASA Astrophysics Data System (ADS)

The ultra-fast dynamics of dielectric oxide materials excited close to the laser-damage threshold is studied by performing transient reflection and transmission pump probe measurements on TiO2, Ta2O5, and HfO2 films. The time-dependent dielectric constant is retrieved taking into account standing-wave effects of both pump and probe. A sub-100-fs transient is followed by a 1-ps transient, during which a sign reversal from negative to positive is observed in the real part of the induced change in the dielectric function, indicating the formation of deep defect states, possibly self-trapped excitons.

Mero, M.; Sabbah, A. J.; Zeller, J.; Rudolph, W.

2005-07-01

288

Application of Metastable Phase Diagrams to Silicate Thin Films for Alternative Gate Dielectrics  

Microsoft Academic Search

Using the concept of metastable phase diagrams, we discuss the microstructure evolution during annealing of amorphous ZrO2-SiO2 and HfO2-SiO2 thin films for gate dielectric applications. These systems are characterized by a low solid solubility, a liquid miscibility gap and a kinetic barrier to the formation of the complex, crystalline silicate. We show that phase partitioning is expected for most compositions.

Susanne Stemmer; Zhiqiang Chen; Carlos G. Levi; Patrick S. Lysaght; Brendan Foran; John A. Gisby; Jeff R. Taylor

2003-01-01

289

Carbon Nanotube Field-Effect Transistors with Integrated Ohmic Contacts and High-kappa Gate Dielectrics  

Microsoft Academic Search

High performance enhancement mode semiconducting carbon nanotube field-effect transistors (CNTFETs) are obtained by combining ohmic metal-tube contacts, high dielectric constant HfO2 films as gate insulators, and electrostatically doped nanotube segments as source\\/drain electrodes. The combination of these elements affords high ON currents, subthreshold swings of ~ 70-80 mV\\/decade, and allows for low OFF currents and suppressed ambipolar conduction. The doped

Ali Javey; Jing Guo; Damon B. Farmer; Qian Wang; Dunwei Wang; Roy G. Gordon; Mark Lundstrom; Hongjie Dai

2004-01-01

290

Effect of interfacial fluorination on the electrical properties of the inter-poly high- k dielectrics  

Microsoft Academic Search

In this paper, the reliabilities and insulating characteristics of the fluorinated aluminum oxide (Al2O3) and hafnium oxide (HfO2) inter-poly dielectric (IPD) are studied. Interface fluorine passivation has been demonstrated in terminating dangling bonds and oxygen vacancies, reducing interfacial re-oxidation and smoothing interface roughness, and diminishing trap densities. Compared with the IPDs without fluorine incorporation, the results clearly indicate that fluorine

Chih-Ren Hsieh; Yung-Yu Chen; Kwung-Wen Lu; Gray Lin; Jen-Chung Lou

2011-01-01

291

Optical properties of the Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings  

NASA Astrophysics Data System (ADS)

Investigations of bilayer and trilayer Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings are presented in this paper. The oxide films were deposited on a heated quartz glass by e-gun evaporation in a vacuum of 5 × 10-3 [Pa] in the presence of oxygen. Depositions were performed at three different temperatures of the substrates: 100 °C, 200 °C and 300 °C. The coatings were deposited onto optical quartz glass (Corning HPFS). The thickness and deposition rate were controlled with Inficon XTC/2 thickness measuring system. Deposition rate was equal to 0.6 nm/s for Al2O3, 0.6 nm - 0.8 nm/s for HfO2 and 0.6 nm/s for SiO2. Simulations leading to optimization of the thin film thickness and the experimental results of optical measurements, which were carried out during and after the deposition process, have been presented. The optical thickness values, obtained from the measurements performed during the deposition process were as follows: 78 nm/78 nm for Al2O3/SiO2 and 78 nm/156 nm/78 nm for Al2O3/HfO2/SiO2. The results were then checked by ellipsometric technique. Reflectance of the films depended on the substrate temperature during the deposition process. Starting from 240 nm to the beginning of visible region, the average reflectance of the trilayer system was below 1 % and for the bilayer, minima of the reflectance were equal to 1.6 %, 1.15 % and 0.8 % for deposition temperatures of 100 °C, 200 °C and 300 °C, respectively.

Marsza?ek, Konstanty; Winkowski, Pawe?; Jaglarz, Janusz

2014-01-01

292

Band Alignment of Plasma-Enhanced ALD High-k Dielectrics on Gallium Nitride  

NASA Astrophysics Data System (ADS)

GaN-based transistors have shown immense promise because of their high saturation velocity and breakdown field, but their performance is limited by the high gate leakage. This limitation is mitigated with the use of metal/high-k oxide/III-N structures. This experiment investigates three promising high-k dielectrics deposited by plasma enhanced ALD: Al2O3, HfO2, and La2O3. The band gaps of these materials are 6.5eV, 5.8eV, and 4.3eV, while the dielectric constants are 9, 20, and 27, respectively. The large band gap associated with Al2O3 reduces the leakage current; however, the lower dielectric constant increases the equivalent oxide thickness. The band alignment of the high-k oxide/GaN interface plays a critical role in determining the confinement properties of semiconductor carriers and ultimately device performance. In situ photoemission gave valence band offsets for Al2O3, HfO2, and La2O3 with GaN as 1.8eV, 1.3eV, and 0.9eV. The results are described by the charge neutrality level and interface dipole models. We also investigated the use of Al2O3 as an interfacial passivation layer between HfO2 and GaN. This research is supported by the Office of Naval Research.

Yang, Jialing; Eller, Brianna; Zhu, Chiyu; Nemanich, Robert

2012-02-01

293

Investigation of interaction between graphene and dielectrics.  

PubMed

The properties of micromechanically exfoliated graphene on different oxide dielectrics--SiO(2), Al(2)O(3), and HfO(2)--are investigated by Raman spectroscopy and AFM measurement. The pristine graphene has stronger adhesion and a higher hole concentration when the dielectric constant of the underlying oxide is higher. It is found that annealing under a high vacuum significantly enhances the adhesion between graphene and the oxides and causes a shift of the Raman G and 2D bands to a higher wavelength. The high vacuum annealing also causes an increase in carrier concentration of up to ten times with a corresponding Fermi level shift of approximately 0.65 eV for graphene on HfO(2). On the other hand, the high vacuum annealing of graphene on SiO(2) induces a biaxial compressive stress as high as 4 GPa on graphene. The results provide understanding on the interaction of graphene and oxides, which is essential for successful realization of graphene-based electronic devices. PMID:20660955

Song, Seung Min; Cho, Byung Jin

2010-08-20

294

The role of microstructure on the optical performance of neutron irradiated dielectric mirrors  

NASA Astrophysics Data System (ADS)

Dielectric mirrors of HfO2/SiO2 and Al2O3/SiO2 designed for optimum reflectivity at 248 nm with 11 and 30 bi-layer coatings, respectively, survived irradiation to 0.1 dpa at 448 K without film cracking or delamination from their sapphire substrates. Subsequent annealing of the irradiated samples resulted in a loss of reflectivity in the HfO2/SiO2 mirror, while the Al2O3/SiO2 type remained unaffected. Microstructural changes that correlate to optical property changes of the mirror are investigated. The amorphous layers of the Al2O3/SiO2 mirror provide greater stability despite increased Al and Si interdiffusion across the film interfaces with increasing dose and post-irradiation annealing temperature. This interdiffusion may have limited the densification of SiO2 in the Al2O3/SiO2 mirror, but no interdiffusion was observed for the HfO2/SiO2 mirror. The thickness changes in the SiO2 layers of the HfO2/SiO2 mirror resulted in a shifting of the peak reflectivity to lower wavelengths. The formation of an amorphous Al–O layer within the substrate is observed in the 0.1 dpa irradiated HfO2/SiO2 mirror, which on further annealing at 573 and 673 K resulted in a buckling-type delamination failures in the mirrors producing a loss in reflectivity.

Leonard, Keith J.; Jellison, Gerald E.; Kumar, N. A. P. Kiran; Snead, Lance L.

2014-02-01

295

Nanosecond pulsed laser damage characteristics of HfO2/SiO2 high reflection coatings irradiated from crystal-film interface.  

PubMed

The nano-precursors in the subsurface of Nd:YLF crystal were limiting factor that decreased the laser-induced damage threshold (LIDT) of HfO(2)/SiO(2) high reflection (HR) coatings irradiated from crystal-film interface. To investigate the contribution of electric-field (E-field) to laser damage originating from nano-precursors and then to probe the distribution of vulnerable nano-precursors in the direction of subsurface depth, two 1064 nm HfO(2)/SiO(2) HR coatings having different standing-wave (SW) E-field distributions in subsurface of Nd:YLF c5424181043036123rystal were designed and prepared. Artificial gold nano-particles were implanted into the crystal-film interface prior to deposition of HR coatings to study the damage behaviors in a more reliable way. The damage test results revealed that the SW E-field rather than the travelling-wave (TW) E-field contributed to laser damage. By comparing the SW E-field distributions and LIDTs of two HR coating designs, the most vulnerable nano-precursors were determined to be concentrated in a thin redeposition layer that is within 100 nm from the crystal-film interface. PMID:23787674

Cheng, Xinbin; Jiao, Hongfei; Lu, Jiangtao; Ma, Bin; Wang, Zhanshan

2013-06-17

296

Dielectric function trajectory of ultrathin gold films  

Microsoft Academic Search

There have been attempts to study the complex refractive index ng of gold films by ellipsometry, but the measurements become unreliable when the average film thickness is below several nanometers, presumably because of optical anisotropy of the thin film. Here, we apply interferometric picometrology to measure ng by analyzing the Fourier-domain anisotropic diffraction of a normal-incidence scanning Gaussian laser beam

Xuefeng Wang; David Nolte

2009-01-01

297

Ultrathin Dielectric Oxide Films On Silicon  

DOEpatents

A method of making a semiconductor structure includes contacting a surface of a semiconductor with a liquid including Zr.sub.4 (OPr.sup.n).sub.16 to form a modified surface, activating the modified surface, and repeating the contacting and activating to form a layer of zirconia on the semiconductor surface.

Klemperer, Walter G. (Champaign, IL); Lee, Jason (Liverpool, GB); Mikalsen, Erik A. (Urbana, IL); Payne, David A. (Champaign, IL)

2004-09-21

298

Performance analysis of silicon nanowire transistors considering effective oxide thickness of high-k gate dielectric  

NASA Astrophysics Data System (ADS)

We have analyzed the effective oxide thickness (EOT) of the dielectric material for which we have optimum performance and the output characteristics of the silicon nanowire transistors by replacing the traditional SiO2 gate insulator with a material that has a much higher dielectric constant (high-k) gate, materials like Si3N4, Al2O3, Y2O3 and HfO2. We have also analyzed the channel conductance, the effect of a change in thickness, the average velocity of the charge carrier and the conductance efficiency in order to study the performance of silicon nanowire transistors in the nanometer region. The analysis was performed using the Fettoy, a numerical simulator for ballistic nanowire transistors using a simple top of the barrier (Natori) approach, which is composed of several matlab scripts. Our results show that hafnium oxide (HfO2) gate insulator material provides good thermal stability, a high recrystallization temperature and better interface qualities when compared with other gate insulator materials; also the effective oxide thickness of HfO2 is found to be 0.4 nm.

Chandra, S. Theodore; Balamurugan, N. B.

2014-04-01

299

Reduced intermolecular interaction in organic ultrathin films  

NASA Astrophysics Data System (ADS)

Submonolayer sensitivity was achieved using in situ ellipsometry to monitor the evolution of the dielectric function of tris(8-hydroxyquinoline)-aluminum(III) (Alq3) layers from submonolayer coverage to thick bulklike layers. The Alq3 layers were deposited under ultrahigh vacuum conditions onto hydrogen passivated silicon. The characteristic vacuum-ultraviolet (VUV) absorption lines of Alq3 were detected using synchrotron radiation as light source. In such ultrathin films the absorption lines corresponding to molecular transitions of the Alq3 are found to be spectrally blueshifted with respect to bulklike layers. We attribute the shift to the effect of reduced intermolecular interaction in the submonolayer regime.

Gordan, O. D.; Himcinschi, C.; Zahn, D. R. T.; Cobet, C.; Esser, N.; Braun, W.

2006-04-01

300

Effective electrical passivation of Ge(100) for high-k gate dielectric layers using germanium oxide  

NASA Astrophysics Data System (ADS)

In search of a proper passivation for high-k Ge metal-oxide-semiconductor devices, the authors have deposited high-k dielectric layers on GeO2, grown at 350-450 °C in O2. ZrO2, HfO2, and Al2O3 were deposited by atomic layer deposition (ALD). GeO2 and ZrO2 or HfO2 intermix during ALD, together with partial reduction of Ge4+. Almost no intermixing or reduction occurs during Al2O3 ALD. Capacitors show well-behaved capacitance-voltage characteristics on both n- and p-Ge, indicating efficient passivation of the Ge/GeOx interface. The density of interface states is typically in the low to mid-1011 cm-2 eV-1 range, approaching state-of-the-art Si/HfO2/matal gate devices.

Delabie, Annelies; Bellenger, Florence; Houssa, Michel; Conard, Thierry; van Elshocht, Sven; Caymax, Matty; Heyns, Marc; Meuris, Marc

2007-08-01

301

Study of roughness evolution and layer stacking faults in short-period atomic layer deposited HfO2/Al2O3 multilayers  

NASA Astrophysics Data System (ADS)

In this work we study the evolution of roughness in interfaces of HfO2/Al2O3 multilayers by x-ray reflectivity. It was found that, besides the reduced adatom surface mobility during atomic layer deposition, an improvement of the interface quality can be achieved upon the stacking of several layers. Although the low roughness of the initial surface could not be recovered, there was a considerable improvement of surface/interface quality along the deposition process. In particular, variations on the growth temperature were not able to tailor the surface quality, if compared to the stacking process. Finally, transmission electron microscopy analysis has shown that local defects can take place among nearly perfect interfaces. Such effect must be taken into account for nanometer-scale device fabrication.

de Pauli, M.; Malachias, A.; Westfahl, H.; Bettini, J.; Ramirez, A.; Huang, G. S.; Mei, Y. F.; Schmidt, O. G.

2011-03-01

302

Influence of Ti substitution on the electrical properties of metal-ferroelectric (BiFeO3)-insulator (HfO2)-silicon structures for nonvolatile memory applications  

NASA Astrophysics Data System (ADS)

Metal-ferroelectric (Ti-substituted BiFeO3)-insulator (HfO2)-semiconductor structures have been fabricated via the cosputtering technique. Ti4+ substitution at the Fe site was investigated through x-ray photoelectron spectra and x-ray diffraction patterns at postannealing temperatures of 500 to 700 °C. The capacitance-voltage memory windows as functions of the insulator film thickness and the dc power for Ti were measured and compared. A memory window of 3.1 V was obtained at a sweep voltage of 8 V under O2-rich conditions. The leakage current and the charge injection effect, especially gate injection, can be greatly improved by Ti substitution. The effects of the postannealing temperature and the substitution amount on the leakage current can be well explained by the defect reaction model.

Pi-Chun Juan, Trevor; Liu, Yu-Wei

2011-05-01

303

Multi-level control of conductive nano-filament evolution in HfO2 ReRAM by pulse-train operations.  

PubMed

Precise electrical manipulation of nanoscale defects such as vacancy nano-filaments is highly desired for the multi-level control of ReRAM. In this paper we present a systematic investigation on the pulse-train operation scheme for reliable multi-level control of conductive filament evolution. By applying the pulse-train scheme to a 3 bit per cell HfO2 ReRAM, the relative standard deviations of resistance levels are improved up to 80% compared to the single-pulse scheme. The observed exponential relationship between the saturated resistance and the pulse amplitude provides evidence for the gap-formation model of the filament-rupture process. PMID:24769626

Zhao, L; Chen, H-Y; Wu, S-C; Jiang, Z; Yu, S; Hou, T-H; Wong, H-S Philip; Nishi, Y

2014-06-01

304

Thermal Conductivity and Stability of HfO2-Y2O3 and La2Zr2O7 Evaluated for 1650 oC Thermal/Environmental Barrier Coating Applications.  

National Technical Information Service (NTIS)

HfO2-Y2O3 and La2Zr2O7 are candidate thermal and environmental barrier coating (T EBC) materials for gas turbine ceramic matrix composite (CMC) combustor applications because of their relatively low thermal conductivity and high temperature capability. In...

D. Zhu N. P. Bansal R. A. Miller

2003-01-01

305

Effects of CF4 Plasma Treatment on pH and pNa Sensing Properties of Light-Addressable Potentiometric Sensor with a 2-nm-Thick Sensitive HfO2 Layer Grown by Atomic Layer Deposition  

NASA Astrophysics Data System (ADS)

We investigated the effect of the carbon tetrafluoride (CF4) plasma treatment on pH and pNa sensing characteristics of a light-addressable potentiometric sensor (LAPS) with a 2-nm-thick HfO2 film grown by atomic layer deposition (ALD). An inorganic CF4 plasma treatment with different times was performed using plasma enhance chemical vapor deposition (PECVD). For pH detection, the pH sensitivity slightly decreased with increasing CF4 plasma time. For pNa detection, the proposed fluorinated HfO2 film on a LAPS device is sensitive to Na+ ions. The linear relationship between pNa sensitivity and plasma treatment time was observed and the highest pNa sensitivity of 33.9 mV/pNa measured from pNa 1 to pNa 3 was achieved. Compared with that of the same structure without plasma treatment, the sensitivity was improved by twofold. The response mechanism of the fluorinated HfO2 LAPS is discussed according to the chemical states determined by X-ray photoelectron spectroscopy (XPS) analysis. The analysis of F 1s, Hf 4f, and O 1s spectra gives evidence that the enhancement of pNa sensitivity is due to the high concentration of incorporated fluorine in HfO2 films by CF4 plasma surface treatment.

Chin, Chi-Hang; Lu, Tseng-Fu; Wang, Jer-Chyi; Yang, Jung-Hsiang; Lue, Cheng-En; Yang, Chia-Ming; Li, Sheng-Shian; Lai, Chao-Sung

2011-04-01

306

Synthesis, integration, and characterization of metal oxide films as alternative gate dielectric materials  

NASA Astrophysics Data System (ADS)

ZrO2 and HfO2 were investigated in this study to replace SiO2 as the potential gate dielectric materials in metal-oxide-semiconductor field effect transistors. ZrO2 and HfO2 films were deposited on p-type Si (100) wafers by an atomic layer chemical vapor deposition (ALCVD) process using zirconium (IV) t-butoxide and hafnium (IV) t-butoxide as the metal precursors, respectively. Oxygen was used alternatively with these metal alkoxide precursors into the reactor with purging and evacuation in between. The as-deposited ZrO2 and HfO2 films were stoichiometric and uniform based on X-ray photoemission spectroscopy and ellipsometry measurements. X-ray diffraction analysis indicated that the deposited films were amorphous, however, the high-resolution transmission electron microscopy showed an interfacial layer formation on the silicon substrate. Time-of-flight secondary ion mass spectrometry and medium energy ion scattering analysis showed significant intermixing between metal oxides and Si, indicating the formation of metal silicates, which were confirmed by their chemical etching resistance in HF solutions. The thermal stability of ZrO2 and HfO2 thin films on silicon was examined by monitoring their decomposition temperatures in ultra-high vacuum, using in-situ synchrotron radiation ultra-violet photoemission spectroscopy. The as-deposited ZrO2 and HfO2 thin films were thermally stable up to 880°C and 950°C in vacuum, respectively. The highest achieveable dielectric constants of as-deposited ZrO 2 and HfO2 were 21 and 24, respectively, which were slightly lower than the reported dielectric constants of bulk ZrO2 and HfO 2. These slight reductions in dielectric constants were attributed to the formation of the interfacial metal silicate layers. Very small hysteresis and interface state density were observed for both metal oxide films. Their leakage currents were a few orders of magnitude lower than that of SiO 2 at the same equivalent oxide thickness. NMOSFETs were also fabricated with the as-deposited metal oxide films, and reasonable ID-V D and IG-VG results were obtained. The electron mobilities were high from devices built using a plasma etching process to pattern the metal oxide films. However, they can be degraded if an HF wet etching process was used due to the large contact resistences. Upon oxygen annealing, the formation of SiOx at the interface improved the thermal stability of the as-deposited metal oxide films, however, lower overall dielectric constant and higher leakage current were observed. Upon ammonia annealing, the formation of SiOxNy improved not only the thermal stability but also reduced the leakage current. However, the overall dielectric constant of the film was still reduced due to the formation of the additional interfacial layer.

Lin, You-Sheng

307

Special Features of the Back-Gate Effects in Ultra-Thin Body SOI MOSFETs  

Microsoft Academic Search

\\u000a Ultra-thin body silicon-on-insulator (SOI) MOSFET is considered to be a strong candidate for ultimate scaling of CMOS technologies,\\u000a because of its excellent suppression of the short-channel effects, even without the use of channel doping. Apart from undoped\\u000a ultra-thin silicon body, nowadays SOI MOSFETs also feature ultra-thin gate high-k gate dielectrics and thin buried oxides.\\u000a These innovating features bring about special

T. Rudenko; V. Kilchytska; J.-P. Raskin; A. Nazarov; D. Flandre

308

Femtosecond pulse damage and predamage behavior of dielectric thin films  

NASA Astrophysics Data System (ADS)

The damage behavior of five different oxide dielectric thin films (Ta2O5, TiO2, Al2O3, HfO2, and SiO2) has been investigated with ultrashort laser pulses with durations from 25 fs to 1 ps. At all pulse durations the damage threshold is well defined and scales with the bandgap energy of the material. The damage behavior can be described with a phenomenological model taking into account multi-photon excitation, impact ionization, and electron relaxation. The temporal evolution of the dielectric constant of the film following the excitation with pulses below the damage threshold has been measured with time-resolved pump-probe spectroscopy. The complex dielectric constant was retrieved from transient reflection and transmission data.

Mero, Mark; Liu, Jianhua; Sabbah, Ali; Jasapara, Jayesh C.; Starke, Kai; Ristau, Detlev; McIver, John K.; Rudolph, Wolfgang G.

2003-05-01

309

Impedance spectroscopic analysis on effects of partial oxidation of TiN bottom electrode and microstructure of amorphous and crystalline HfO2 thin films on their bipolar resistive switching.  

PubMed

The electrical resistance switching (RS) properties of amorphous HfO2 (a-HfO2) and crystalline HfO2 (c-HfO2) thin films grown on a TiN substrate via atomic layer deposition were examined using DC current-voltage (I-V) sweep and AC impedance spectroscopic (IS) analyses. The rapid thermal annealing of the a-HfO2 film at 500 °C under a N2 atmosphere for 5 min crystallized the HfO2 film and induced an interfacial TiON barrier layer. The a-HfO2 sample showed fluent bipolar RS performance with a high on/off ratio (? 500), whereas the c-HfO2 sample showed a much lower on/off ratio (

Yoon, Ji-Wook; Yoon, Jung Ho; Lee, Jong-Heun; Hwang, Cheol Seong

2014-06-21

310

Impedance spectroscopic analysis on effects of partial oxidation of TiN bottom electrode and microstructure of amorphous and crystalline HfO2 thin films on their bipolar resistive switching  

NASA Astrophysics Data System (ADS)

The electrical resistance switching (RS) properties of amorphous HfO2 (a-HfO2) and crystalline HfO2 (c-HfO2) thin films grown on a TiN substrate via atomic layer deposition were examined using DC current-voltage (I-V) sweep and AC impedance spectroscopic (IS) analyses. The rapid thermal annealing of the a-HfO2 film at 500 °C under a N2 atmosphere for 5 min crystallized the HfO2 film and induced an interfacial TiON barrier layer. The a-HfO2 sample showed fluent bipolar RS performance with a high on/off ratio (~500), whereas the c-HfO2 sample showed a much lower on/off ratio (<~10), but its switching uniformity was better than that of a-HfO2. Such critical differences can be mainly attributed to the absence and presence of the TiON barrier layer in the a-HfO2 and c-HfO2 samples, respectively. The AC IS especially enabled the resistance states of the HfO2/Pt interface and the HfO2/TiN interface to be separately examined during one complete switching cycle of each sample. Although the Pt/c-HfO2 interface has a Schottky barrier in the pristine state, it disappeared once the c-HfO2 was electroformed and was not recovered even after the reset step. In contrast, the Pt/a-HfO2 interface partly recovered the Schottky barrier after the reset.

Yoon, Ji-Wook; Yoon, Jung Ho; Lee, Jong-Heun; Hwang, Cheol Seong

2014-05-01

311

Dielectric response of sputtered transition metal oxides  

NASA Astrophysics Data System (ADS)

We have investigated the dielectric properties of thin layers of five oxides of transition metals (Ta2O5, HfO2, ZrO2, (ZrO2)0.91(Y2O3)0.09, and Sn0.2Zr0.2Ti0.6O2) sputtered from ceramic targets at different pressures. We find that layers deposited at low pressure behave as expected from literature, whereas layers deposited at high pressure all exhibit an anomalous dielectric response similar to that reported for the so-called ``colossal'' dielectric constant materials. The characterization of the thickness, frequency, and temperature dependence of the capacitance, as well as the comparison of film properties before and after annealing show that the anomalous dielectric response is due to quenched-in vacancies that act as dopants and cause the insulating layers to behave as semiconductors. An increase in quenched-in vacancies concentration with sputtering pressure results in a transition from normal to anomalous dielectric response and gradual increase in layer conductivity. In contrast, the refractive index does not depend on sputtering pressure. This observation indicates the possible application of these materials as transparent coatings with a tunable electrical conductivity.

Iosad, N. N.; Ruis, G. J.; Morks, E. V.; Morpurgo, A. F.; van der Pers, N. M.; Alkemade, P. F. A.; Sivel, V. G. M.

2004-06-01

312

Low-Frequency Noise of Strained and Non-Strained n-Channel Tri-Gate FinFETs With Different Gate Dielectrics  

NASA Astrophysics Data System (ADS)

The influence of different front gate Hf-based high-k dielectrics (HfSiON/SiO2 and HfO2/SiO2) on the shape of the low-frequency noise spectra for n-channel tri-gate FinFETs processed in standard silicon-on-insulator (SOI) substrates, and global Strained Si Directly On Insulator (sSOI) wafers with/without Selective Epitaxial Grown (SEG) source and drain regions is studied. For different process splits the concentration distributions of slow traps over the thickness of the gate dielectric are estimated and it is shown that these distributions depend on the dielectric type.

Lukyanchikova, N.; Garbar, N.; Kudina, V.; Smolanka, A.; Simoen, E.; Claeys, C.

2009-04-01

313

Interfaces of high- k dielectrics on GaAs: Their common features and the relationship with Fermi level pinning (Invited Paper)  

Microsoft Academic Search

Numerous metal oxides have been studied worldwide as possible high-k gate dielectric candidates for MOS devices on alternative semiconductor materials (Ge, III\\/V compounds). We will discuss thermal and plasma-enhanced atomic layer deposition (ALD) of a few materials, HfO2 and Al2O3. We will spend some attention to characteristic features of the growth process and specific growth precursors as this is known

Matty Caymax; Guy Brammertz; Annelies Delabie; Sonja Sioncke; Dennis Lin; Marco Scarrozza; Geoffrey Pourtois; Wei-E Wang; Marc Meuris; Marc Heyns

2009-01-01

314

Dramatic improvement of V\\/sub fb\\/, shift and G\\/sub m\\/\\/sup max\\/ with ultra-thin and ultra-low-leakage SiN-based SiON gate dielectrics  

Microsoft Academic Search

The understanding of the mechanism of Delta Vfb and the improvement of [N]-DeltaVfb relationship are essential for realizing SiON film with superior device performance. By forming the smooth SiN film with high-density NequivSi3 structure and suppressing the deterioration of Si-N network due to oxidation, SiON films with dramatic improvement on [N]-DeltaVfb relationship with ultra-thin EOT (0.71 nm), ultra-low leakage current

D. Matsushita; K. Muraoka; Y. Nakasaki; K. Kato; S. Kikuchi; K. Sakuma; Y. Mitani; K. Eguchi; M. Takayanagi

2005-01-01

315

High-temperature phase stability of hafnium aluminate films for alternative gate dielectrics  

NASA Astrophysics Data System (ADS)

Hafnium aluminate films with different compositions were deposited at room temperature by jet vapor deposition. The as-deposited films were amorphous. After annealing at 1100 °C, the microstructure of the films was analyzed by high-resolution transmission electron microscopy, electron diffraction and electron energy loss spectroscopy (EELS). The crystalline phase in pure HfO2 films was monoclinic. With an increase in the Al content in the films, the amount of metastable HfO2 with a tetragonal distorted fluorite structure increased. In addition, the grain sizes decreased, making the detection of crystallization by x-ray diffraction difficult. No crystalline Al2O3 phase could be unambiguously detected in electron diffraction patterns in films with up to 30 mol % Al2O3. However, an Al-rich intergranular phase was identified by EELS. Films with ~64 mol % Al2O3 crystallized as tetragonal HfO2 and metastable cubic Al2O3 with the spinel structure. The complex microstructures of the films should be considered in the interpretation of their dielectric and electrical properties after high temperature anneals.

Yang, Yan; Zhu, Wenjuan; Ma, T. P.; Stemmer, Susanne

2004-04-01

316

High-k dielectrics on (100) and (110) n-InAs: Physical and electrical characterizations  

NASA Astrophysics Data System (ADS)

Two high-k dielectric materials (Al2O3 and HfO2) were deposited on n-type (100) and (110) InAs surface orientations to investigate physical properties of the oxide/semiconductor interfaces and the interface trap density (Dit). X-ray photoelectron spectroscopy analyses (XPS) for native oxides of (100) and (110) as-grown n-InAs epi wafers show an increase in As-oxide on the (100) surface and an increase in InOx on the (110) surface. In addition, XPS analyses of high-k (Al2O3 and HfO2) on n-InAs epi show that the intrinsic native oxide difference between (100) and (110) epi surfaces were eliminated by applying conventional in-situ pre-treatment (TriMethyAluminium (TMA)) before the high-k deposition. The capacitance-voltage (C-V) characterization of HfO2 and Al2O3 MOSCAPs on both types of n-InAs surfaces shows very similar C-V curves. The interface trap density (Dit) profiles show Dit minima of 6.1 × 1012/6.5 × 1012 and 6.6 × 1012/7.3 × 1012 cm-2 eV-1 for Al2O3 and HfO2, respectively for (100) and (110) InAs surfaces. The similar interface trap density (Dit) on (100) and (110) surface orientation were observed, which is beneficial to future InAs FinFET device with both (100) and (110) surface channel orientations present.

Wang, C. H.; Doornbos, G.; Astromskas, G.; Vellianitis, G.; Oxland, R.; Holland, M. C.; Huang, M. L.; Lin, C. H.; Hsieh, C. H.; Chang, Y. S.; Lee, T. L.; Chen, Y. Y.; Ramvall, P.; Lind, E.; Hsu, W. C.; Wernersson, L.-E.; Droopad, R.; Passlack, M.; Diaz, C. H.

2014-04-01

317

Calculation of the electron mobility in III-V inversion layers with high-? dielectrics  

NASA Astrophysics Data System (ADS)

We calculate the electron mobility for a metal-oxide-semiconductor system with a metallic gate, high-? dielectric layer, and III-V substrate, including scattering with longitudinal-optical (LO) polar-phonons of the III-V substrate and with the interfacial excitations resulting from the coupling of insulator and substrate optical modes among themselves and with substrate plasmons. In treating scattering with the substrate LO-modes, multisubband dynamic screening is included and compared to the dielectric screening in the static limit and with the commonly used screening model obtained by defining an effective screening wave vector. The electron mobility components limited by substrate LO phonons and interfacial modes are calculated for In0.53Ga0.47As and GaAs substrates with SiO2 and HfO2 gate dielectrics. The mobility components limited by the LO-modes and interfacial phonons are also investigated as a function of temperature. Scattering with surface roughness, fixed interface charge, and nonpolar-phonons is also included to judge the relative impact of each scattering mechanism in the total mobility for In0.53Ga0.47As with HfO2 gate dielectric. We show that InGaAs is affected by interfacial-phonon scattering to an extent larger than Si, lowering the expected performance, but probably not enough to question the technological relevance of InGaAs.

O'Regan, T. P.; Fischetti, M. V.; Sorée, B.; Jin, S.; Magnus, W.; Meuris, M.

2010-11-01

318

Dielectric function of warm dense gold  

Microsoft Academic Search

Single-state measurements of the broadband (450-800 nm) dielectric function of gold using a supercontinuum probe are reviewed. These measurements have demonstrated the first evidence of the existence of band structure in ultrathin gold foils isochorically heated by a femtosecond laser pulse to energy densities of 106-107 J\\/kg. The Drude component of the dielectric function increases with energy density while the

Y. Ping; D. Hanson; I. Koslow; T. Ogitsu; D. Prendergast; E. Schwegler; G. Collins; A. Ng

2008-01-01

319

Effect of Postdeposition Annealing Temperatures on Electrical Characteristics of Molecular-Beam-Deposited HfO2 on n-InAs/InGaAs Metal--Oxide--Semiconductor Capacitors  

NASA Astrophysics Data System (ADS)

The electrical characteristics of molecular-beam-deposited HfO2/n-InAs/InGaAs metal--oxide--semiconductor capacitors with different postdeposition annealing (PDA) temperatures (400--550 °C) are investigated. Results show that the sample with the PDA temperature of 500 °C exhibits the best capacitance--voltage (C--V) behavior with small frequency dispersion and small hysteresis. The X-ray photoelectron spectroscopy (XPS) spectra show the reduction of the amount of As-related oxides to below the XPS detection level when the PDA temperature is up to 500 °C. As the PDA temperature was increased to above 500 °C, As and In atoms seem to diffuse significantly into HfO2, resulting in the degradation of C--V behavior.

Trinh, Hai-Dang; Lin, Yueh-Chin; Wang, Huan-Chung; Chang, Chia-Hua; Kakushima, Kuniyuki; Iwai, Hiroshi; Kawanago, Takamasa; Lin, Yan-Gu; Chen, Chi-Ming; Wong, Yuen-Yee; Huang, Guan-Ning; Hudait, Mantu; Chang, Edward Yi

2012-02-01

320

High dielectric constant oxides on III-V complementary metal-oxide-semiconductors  

NASA Astrophysics Data System (ADS)

Suitable gate dielectrics are needed for III-V channel metal-oxide-semiconductor field-effect transistors (MOSFETs). III-V semiconductor surfaces tend to have high interface trap state density (Dit). High quality gate dielectrics require a high dielectric constant, a stable interface, and low Dit. The major challenges are scaling down the dielectric to achieve high capacitance densities, understanding defects at the oxide/semiconductor interface, and developing techniques to passivate Dit at the interface. By using nitrogen plasma pre-treatment passivation technique, MOSCAPs with ALD HfO 2 directly on InGaAs as high-k gate stack, with accumulation capacitance density 2.4 mu F/cm2 (EOT=0.6 nm) and 2.5 x 10 12 cm2 eV-1 midgap Dit have been achieved.

Chobpattana, Varistha

321

Dielectric tensors of high-k Pbnm perovskites from first principles  

NASA Astrophysics Data System (ADS)

Among the materials under consideration for future high-k dielectrics in MOSFET and other microelectronic devices are several perovskites having space group Pbnm. Among these are LaLuO3, SrBO3 (B = Zr, Hf), AScO3 (A = La, Pr, Nd, Sm, Gd, Tb, Dy), and LaB1/2Zr1/2O3 (B = Ca, Mg) (with lower symmetry), which are all compatible with growth on silicon and can have higher dielectric constants than HfO2. Using first-principles DFT methods with ultrasoft pseudopotentials and GGA energy functionals, we compute the dielectric tensors, structural properties, and phonon spectra of these materials. We analyze the dependence of these properties on chemical composition, and compare with experiments where possible. We also focus on correlation between dielectric tensor anisotropy and octahedra rotation angles.

Coh, Sinisa; Vanderbilt, David

2009-03-01

322

Physics of ultrathin photovoltaics  

NASA Astrophysics Data System (ADS)

The authors consider physical properties of ultrathin photovoltaics with thickness (<~1 ?m) smaller than both the depletion width and diffusion length, applicable to the cases of amorphous, polycrystalline, and nanostructured devices. Three phenomena underlie the unique physics of such systems: (1) lateral screening by conducting electrodes, (2) leakiness due to defect assisted tunneling, and (3) gigantic capacitive energy conducive to shunting breakdown. The authors give numerical estimates and discuss practical implications of these phenomena.

Karpov, V. G.; Cooray, M. L. C.; Shvydka, Diana

2006-10-01

323

Effect of rotation, gate-dielectric and SEG on the noise behavior of advanced SOI MuGFETs  

NASA Astrophysics Data System (ADS)

In this work the influence of Selective Epitaxial Growth (SEG), high- k gate-dielectric and rotation of the channel on the low frequency (LF)-noise is investigated. The carrier number fluctuations dominate the 1/ f noise for all the devices studied. An unusual effective trap density profile is found. It decays with a larger distance from the interface. This implies a higher trap density in the interfacial SiO 2-layer, compared with the high- k dielectric. The shape of the profile is different for a HfSiON gate-dielectric compared with a HfO 2 gate-dielectric. Higher trap densities are found for the latter. The Selective Epitaxial Growth (SEG) and channel orientation show only a negligible impact on the noise behavior when a HfSiON-dielectric is used.

Put, S.; Mehta, H.; Collaert, N.; Van Uffelen, M.; Leroux, P.; Claeys, C.; Lukyanchikova, N.; Simoen, E.

2010-02-01

324

Thermal Conductivity and Stability of HfO2-Y2O3 and La2Zr2O7 Evaluated for 1650 C Thermal/Environmental Barrier Coating Applications  

NASA Technical Reports Server (NTRS)

HfO2-Y2O3 and La2Zr2O7 are candidate thermal and environmental barrier coating (T/EBC) materials for gas turbine ceramic matrix composite (CMC) combustor applications because of their relatively low thermal conductivity and high temperature capability. In this paper, thermal conductivity and high temperature stability of hot-pressed and plasma sprayed specimens with representative partially-stabilized and fully-cubic HfO2-Y2O3 compositions and La2Zr2O7 were evaluated at temperatures up to 1700 C using a steady-state laser heat-flux technique. Sintering behavior of the plasmasprayed coatings was determined by monitoring the thermal conductivity increases during a 20-hour test period at various temperatures. Durability and failure mechanisms of the HfO2-Y2O3 and La2Zr2O7 coatings on mullite/SiC hexoloy or SiC/SiC CMC substrates were investigated at 1650 C under thermal gradient cyclic conditions. Coating design and testing issues for the 1650 C thermal/environmental barrier coating applications are also discussed.

Zhu, Dong-Ming; Bansal, Narottam P.; Miller, Robert A.

2003-01-01

325

STM characterization of ultrathin Si oxynitride layers  

NASA Astrophysics Data System (ADS)

Minor defects in thin gate dielectric films play dominant roles in both the performance and reliability of metal-oxide-semiconductor devices. In this work, we used STM and STS to examine the local electric properties of ultrathin Si oxynitride layers. The oxynitride layers were thermally grown on clean Si(001)-2x1 surfaces under 2x10-6 Torr NO pressure at 650^circC. Under these growth conditions, one or two atomic layers of Si on the Si surface react with NO [1]. STM images of the oxynitrided Si surface showed atomic-scale spots (0.3-2 nm in diameter) at a density of about 1x10^14 cm-2. From most of these spots, normal I-V curves explained by electron transport from the tip to the sample were observed. From a few spots, negative differential resistance (NDR) and plateau curves were observed in the positive sample bias region. These electric properties indicated atomic-scale localization on the spots. We considered that the NDR and plateau features were caused by defect states below or near the SiON conduction band edge. We found that the defect density in the oxynitride layer increased with the NO exposure time and was larger than that of the ultrathin Si oxide layer. [1] N. Miyata, H. Watanabe, and M. Ichikawa, Appl. Phys. Lett. 76, 3561 (2000). This work was partly supported by NEDO.

Miyata, Noriyuki; Ichikawa, Masakazu

2001-03-01

326

Tunneling current and thickness inhomogeneities of ultrathin aluminum oxide films in magnetic tunneling junctions  

Microsoft Academic Search

Tunneling current and thickness inhomogeneities of ultrathin aluminum oxide layers of magnetic tunnel junctions are studied by conducting atomic force microscopy (CAFM). The current inhomogeneities are attributed to thickness inhomogeneities on a nanometer scale. Thickness distributions are derived from the current distributions, using the Simmons’ tunneling model by assuming a constant and uniform barrier height. It is shown that dielectric

E. Z. Luo; S. K. Wong; A. B. Pakhomov; J. B. Xu; I. H. Wilson; C. Y. Wong

2001-01-01

327

Tunneling current and thickness inhomogeneities of ultrathin aluminum oxide films in magnetic tunneling junctions  

Microsoft Academic Search

Tunneling current and thickness inhomogeneities of ultrathin aluminum oxide layers of magnetic tunnel junctions are studied by conducting atomic force microscopy (CAFM). The current inhomogeneities are attributed to thickness inhomogeneities on a nanometer scale. Thickness distributions are derived from the current distributions, using the Simmons' tunneling model by assuming a constant and uniform barrier height. It is shown that dielectric

E. Z. Luo; S. K. Wong; A. B. Pakhomov; J. B. Xu; I. H. Wilson; C. Y. Wong

2001-01-01

328

Atomic layer deposition of high-k dielectrics on single-walled carbon nanotubes: a Raman study  

NASA Astrophysics Data System (ADS)

Single-wall carbon nanotubes (SWCNTs) have great potential to become the channel material for future high-speed transistor technology. However, to realize a carbon nanotube field effect transistor (CNTFET) with excellent gate control, the high-k dielectrics between the CNT and the metal gate must have superb electrical properties and extremely high uniformity. Thus it is essential to understand the interactions between high-k materials and the SWCNTs to effectively control the transistor characteristics. In this study, we investigate the effects of atomic layer deposited (ALD) high-k dielectrics (Al2O3 and HfO2) on SWCNTs using Raman spectroscopy. We subjected the SWCNTs to various ALD cycles and studied the nucleation and growth of ALD dielectrics at defect sites using scanning electron microscopy and transmission electron microscopy images. We analyzed these samples using Raman spectroscopy and x-ray photoelectron spectroscopy. The Raman peak shifts of the G-peak and the 2D (G?) peaks suggest doping and stress induced effects on the CNTs by the surrounding high-k oxide environment. Trends in the G-peak FWHM and G/D-peak ratios were identified and compared between Al2O3 and HfO2. We confirmed the ALD-deposited HfO2 is polycrystalline using x-ray diffraction and analyzed dielectric-CNT bonding states using XPS measurements. This study provides insights on the effects of ALD high-k materials on SWCNTs for future high-speed transistor applications.

Suriyasena Liyanage, Luckshitha; Cott, Daire J.; Delabie, Annelies; Van Elshocht, Sven; Bao, Zhenan; Wong, H.-S. Philip

2013-06-01

329

Growth and structure control of HfO2-x films with cubic and tetragonal structures obtained by ion beam assisted deposition  

NASA Astrophysics Data System (ADS)

Hafnium oxide films were grown by ion beam assisted deposition on water-cooled Si (100) substrates, under conditions of oxygen starvation, using hafnium vapor and an oxygen ion beam. The transport ratio (TR), i.e., the ratio between the arrival rate of hafnium to that of oxygen, was varied between 0.5 and 10, and ion energy was varied between 1 and 20 keV. The films were analyzed using x-ray diffraction and x-ray photoelectron spectroscopy. Films having the CaF2 cubic structure with a lattice parameter of about 0.512 nm were repeatedly obtained. In addition, at 20 keV ion energy and TR values of 4 and above, films with a tetragonal structure were obtained. The latter structure, believed to be a distortion of the cubic structure, has a c/a ratio of 1.01 and its space group is considered to be different from the high temperature tetragonal HfO2 structure. The new tetragonal structure also presents high Knoop hardness, with values between 15 and 25 GPa. Substrate rotation speed was found to affect the structure and the orientation of the films. All films exhibit a stoichiometry in the vicinity of HfO1.6, with the tetragonal films apparently being Hf2O3. These structures are attributed to a very fast cooling rate during film formation. Films deposited without substrate water cooling, or with substrate heating up to 500 °C contain a large component of the monoclinic phase. The new cubic and tetragonal structures are stable at room temperature and upon annealing up to 450 °C in vacuum, but convert to the monoclinic structure upon annealing at 500 °C in air, indicating that their low oxygen content is a key factor for their stability.

Manory, Rafael R.; Mori, Takanori; Shimizu, Ippei; Miyake, Shoji; Kimmel, Giora

2002-03-01

330

Ultrathin metallized PBI paper  

NASA Technical Reports Server (NTRS)

A study to determine the feasibility of preparing ultrathin papers with a target weight of 3.5 g/m squared from polybenzimidazole (PBI) fibrids was undertaken. Small hand sheets of target weight were fabricated. They were light brown, low density materials with sufficient strength to be readily handleable. Characterization of these sheets included strength, fold endurance, thermal gravimetric analysis in air and nitrogen and photomicrographs. Two different batches of PBI fibrids were studied and differences in fabrication performance were noted. In neither case could target weight papers be prepared using conventional paper making techniques.

Chenevey, E. C.

1978-01-01

331

Growth and electrical properties of spin coated ultrathin ZrO2 films on silicon  

NASA Astrophysics Data System (ADS)

Ultrathin (<50 nm) zirconium oxide (ZrO2) films are being intensively studied as high-k dielectrics for future metal-oxide-semiconductor (MOS) technology. In this paper, ultrathin ZrO2 films are deposited on silicon substrates by spin on deposition technique and annealed at 700 °C for different duration. The phase formation and morphological study have been performed by x-ray diffraction and scanning electron microscopy, respectively. Electrical properties of the films are investigated. The threshold voltages of the MOS structure were found to vary from -1.5 V to -2.5 V as the annealing time increases. The dielectric constants of the films are found to be 7.2-7.67 at 1 KHz. Leakage current of the films is found to increase with the annealing time. The dielectric breakdown field of the film is found to be 6.29-8.15 MV/cm.

Dutta, Shankar; Pandey, Akhilesh; Yadav, Isha; Thakur, O. P.; Kumar, A.; Pal, Ramjay; Chatterjee, Ratnamala

2013-07-01

332

Enhancement of absorption and color contrast in ultra-thin highly absorbing optical coatings  

NASA Astrophysics Data System (ADS)

Recently a new class of optical interference coatings was introduced which comprises ultra-thin, highly absorbing dielectric layers on metal substrates. We show that these lossy coatings can be augmented by an additional transparent subwavelength layer. We fabricated a sample comprising a gold substrate, an ultra-thin film of germanium with a thickness gradient, and several alumina films. The experimental reflectivity spectra showed that the additional alumina layer increases the color range that can be obtained, in agreement with calculations. More generally, this transparent layer can be used to enhance optical absorption, protect against erosion, or as a transparent electrode for optoelectronic devices.

Kats, Mikhail A.; Byrnes, Steven J.; Blanchard, Romain; Kolle, Mathias; Genevet, Patrice; Aizenberg, Joanna; Capasso, Federico

2013-09-01

333

CONDENSED MATTER: ELECTRONICSTRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Robust Low Voltage Program-Erasable Cobalt-Nanocrystal Memory Capacitors with Multistacked Al2O3\\/HfO2\\/Al2O3 Tunnel Barrier  

Microsoft Academic Search

An atomic-layer-deposited Al2O3\\/HfO2\\/Al2O3 (A\\/H\\/A) tunnel barrier is investigated for Co nanocrystal memory capacitors. Compared to a single Al2O3 tunnel barrier, the A\\/H\\/A barrier can significantly increase the hysteresis window, i.e., an increase by 9 V for ±12 V sweep range. This is attributed to a marked decrease in the energy barriers of charge injections for the A\\/H\\/A tunnel barrier. Further,

Zhong-Wei Liao; Hong-Yan Gou; Yue Huang; Qing-Qing Sun; Shi-Jin Ding; Wei Zhang; Shi-Li Zhang

2009-01-01

334

Optical properties and damage thresholds of dielectric UV\\/VUV coatings deposited by conventional evaporation, IAD, and IBS  

Microsoft Academic Search

Conventional evaporation as well as IAD and IBS processes were used to develop low-loss dielectric mirrors and antireflection coatings for the wavelength range 130 to 250 nm. First, single layers of SiO2, Al2O3, HfO2, AlF3, MgF2, LaF3, NdF3, and GdF3 were deposited. The refractive indices, extinction coefficients and packing densities of the layers were determined by spectrophotometric methods in order

Jurgen Kolbe; H. Kessler; T. Hofmann; F. Meyer; Harald Schink; Detlev Ristau

1992-01-01

335

MOS Ge Diodes Based on High ? Gate Dielectrics Grown by MBE and ALD  

NASA Astrophysics Data System (ADS)

Germanium-based CMOS technology is gaining importance due to its high carrier mobility. In this work high ? gate-dielectrics, Al2O3, HfO2, Y2O3 and Ga2O3(Gd2O3) grown by MBE and ALD were investigated as passivation layers on n type Ge(100). Thermal stability of the MOS diodes was examined after various anneals. Prior to dielectric depositions surface pretreatments were applied to reduce the unwanted GeOx interfacial layer, and to improve electrical properties. Frequency dispersion of C-V curves was reduced by using a 350^oC preclean process, compared to the sample without precleaning. The leakage current density of ALD grown HfO2 (6.8nm) is 4.6×10-6 A/cm^2 with ? of 10.5. The improved CV curve was attributed to less GeOx formed at substrate and oxide interface, as confirmed by XPS analysis. However, with higher cleaning temperature over 400^oC, the CV curves showed additional inversion capacitance, possibly due to minority carriers from defect states near the interface.

Lee, Kun Yu; Lee, W. C.; Lin, T. D.; Lee, C. S.; Chang, Y. C.; Lee, Y. J.; Huang, M. L.; Wu, Y. D.; Hong, M.; Kwo, J.

2007-03-01

336

Femtosecond pulse damage behavior of oxide dielectric thin films  

NASA Astrophysics Data System (ADS)

Pulse duration and band-gap scaling of the laser breakdown threshold fluence of oxide dielectrics were measured using various (TiO2, Ta2O5, HfO2, Al2O3, and SiO2) single layer thin films. The observed scaling with pulse duration was explained by an empirical model including multi-photon and avalanche ionization, and conduction band electron decay. The results suggest the formation of self-trapped excitons on a sub-ps time-scale, which can cause significant energy transfer to the lattice. At constant pulse duration, the band-gap scaling was found to be approximately linear. This linear scaling can be explained by the Keldysh photo-ionization theory and avalanche ionization in the flux-doubling approximation.

Mero, Mark; Liu, Jianhua; Zeller, Joachim; Rudolph, Wolfgang G.; Starke, Kai; Ristau, Detlev

2004-06-01

337

Ultrathin antibiotic walled microcapsules.  

PubMed

Ultrathin microcapsules comprised of anionic polyelectrolytes (PE) and a polycationic aminoglycoside (AmG) antibiotic drug were prepared by depositing PE/AmG multilayers on zinc oxide (ZnO) colloid particles using the layer-by-layer self-assembly technique and subsequently dissolving the ZnO templated cores. The polyelectrolytes, dextran sulfate sodium (DxS) and poly(styrenesulfonate) (PSS), were selected owing to their different backbone structure. An aminoglycoside, tobramycin sulfate (TbS), was used for studying DxS/TbS or PSS/TbS multilayer films. The multilayer growth on ZnO cores was characterized by alternating zeta potential values that were different for the DxS/TbS and PSS/TbS multilayers due to the PE chemistry and its interaction with Zn(2+) ions. Transmission and scanning electron microscopy provide evidence of PE/TbS multilayer coating on ZnO core particles. The slow acid-decomposition of the ZnO cores using weak organic acids and the presence of sufficient quantity of Zn(2+) in the dispersion were required to produce antibiotic multilayer capsules. There was no difference in the morphological characteristics of the two types of capsules; although, the yield for [PSS/TbS](5) capsules was significantly higher than for [DxS/TbS](5) capsules which was related to the physicochemical properties of DxS/TbS/Zn(2+) and PSS/TbS/Zn(2+) complexes forming the capsule wall. The TbS quantity in the multilayer films was determined using a quartz crystal microbalance and high performance liquid chromatography techniques which showed less TbS loading in both, capsules and multilayers on planar gold substrate, than the theoretical DxS:TbS or PSS:TbS stoichiometric ratio. The decomposition of the [PE/TbS](6) multilayers was fastest in physiological buffer followed by mannitol and water. The decomposition rate of the [PSS/TbS](6) multilayers was slower than [DxS/TbS](6) monolayers. The incomplete decomposition of DxS/TbS under saline conditions suggests the major role of hydrogen bonding for stability of DxS/TbS multilayers. A combination of hydrogen bonding and hydrophobic interaction between phenyl rings in PSS was responsible for PSS/TbS multilayer stability. In vivo studies in rabbits highlight the safety and sustained drug delivery potential of the PE/AmG microcapsules. The antibiotic walled ultrathin capsules presented here are suitable for sustained ophthalmic antibiotic delivery. PMID:15638525

Khopade, Ajay J; Arulsudar, N; Khopade, Surekha A; Hartmann, J

2005-01-01

338

Ultrathin and broadband high impedance surface absorbers based on metamaterial substrates.  

PubMed

An ultrathin and simultaneously broadband high impedance surface absorber based on a metamaterial (MM) substrate is presented at microwave frequencies. The MM substrate is designed using metallic split ring resonators (SRRs) vertically embedded into a dielectric slab. Both the simulated and experimental results display two absorption peaks and an expanded absorption bandwidth of less than -10 dB compared to conventional ultrathin absorbers. By analyzing the field distributions and the substrate impedance characteristics, it is found that this feature is mainly related to the LC resonance of the substrate caused by the embedded SRRs. Our results demonstrate the great feasibility of broadening the absorption bandwidth of the ultrathin high impedance surface absorbers by the MMs incorporation. PMID:22714239

Pang, Yongqiang; Cheng, Haifeng; Zhou, Yongjiang; Li, Zenggnag; Wang, Jun

2012-05-21

339

Conformal surface plasmons propagating on ultrathin and flexible films  

PubMed Central

Surface plasmon polaritons (SPPs) are localized surface electromagnetic waves that propagate along the interface between a metal and a dielectric. Owing to their inherent subwavelength confinement, SPPs have a strong potential to become building blocks of a type of photonic circuitry built up on 2D metal surfaces; however, SPPs are difficult to control on curved surfaces conformably and flexibly to produce advanced functional devices. Here we propose the concept of conformal surface plasmons (CSPs), surface plasmon waves that can propagate on ultrathin and flexible films to long distances in a wide broadband range from microwave to mid-infrared frequencies. We present the experimental realization of these CSPs in the microwave regime on paper-like dielectric films with a thickness 600-fold smaller than the operating wavelength. The flexible paper-like films can be bent, folded, and even twisted to mold the flow of CSPs.

Shen, Xiaopeng; Cui, Tie Jun; Martin-Cano, Diego; Garcia-Vidal, Francisco J.

2013-01-01

340

Conformal surface plasmons propagating on ultrathin and flexible films.  

PubMed

Surface plasmon polaritons (SPPs) are localized surface electromagnetic waves that propagate along the interface between a metal and a dielectric. Owing to their inherent subwavelength confinement, SPPs have a strong potential to become building blocks of a type of photonic circuitry built up on 2D metal surfaces; however, SPPs are difficult to control on curved surfaces conformably and flexibly to produce advanced functional devices. Here we propose the concept of conformal surface plasmons (CSPs), surface plasmon waves that can propagate on ultrathin and flexible films to long distances in a wide broadband range from microwave to mid-infrared frequencies. We present the experimental realization of these CSPs in the microwave regime on paper-like dielectric films with a thickness 600-fold smaller than the operating wavelength. The flexible paper-like films can be bent, folded, and even twisted to mold the flow of CSPs. PMID:23248311

Shen, Xiaopeng; Cui, Tie Jun; Martin-Cano, Diego; Garcia-Vidal, Francisco J

2013-01-01

341

High-performance, highly bendable MoS2 transistors with high-k dielectrics for flexible low-power systems.  

PubMed

While there has been increasing studies of MoS2 and other two-dimensional (2D) semiconducting dichalcogenides on hard conventional substrates, experimental or analytical studies on flexible substrates has been very limited so far, even though these 2D crystals are understood to have greater prospects for flexible smart systems. In this article, we report detailed studies of MoS2 transistors on industrial plastic sheets. Transistor characteristics afford more than 100x improvement in the ON/OFF current ratio and 4x enhancement in mobility compared to previous flexible MoS2 devices. Mechanical studies reveal robust electronic properties down to a bending radius of 1 mm which is comparable to previous reports for flexible graphene transistors. Experimental investigation identifies that crack formation in the dielectric is the responsible failure mechanism demonstrating that the mechanical properties of the dielectric layer is critical for realizing flexible electronics that can accommodate high strain. Our uniaxial tensile tests have revealed that atomic-layer-deposited HfO2 and Al2O3 films have very similar crack onset strain. However, crack propagation is slower in HfO2 dielectric compared to Al2O3 dielectric, suggesting a subcritical fracture mechanism in the thin oxide films. Rigorous mechanics modeling provides guidance for achieving flexible MoS2 transistors that are reliable at sub-mm bending radius. PMID:23668386

Chang, Hsiao-Yu; Yang, Shixuan; Lee, Jongho; Tao, Li; Hwang, Wan-Sik; Jena, Debdeep; Lu, Nanshu; Akinwande, Deji

2013-06-25

342

Femtosecond dynamics of highly excited dielectric thin films  

NASA Astrophysics Data System (ADS)

The dielectric constant of several oxide dielectric thin-films (TiO2, Ta2O5 and HfO2) excited close to the laser-induced damage threshold is retrieved from reflection and transmission measurements with a 40-fs time resolution. The experiments were compared with the results of a numerical solution of the coupled Boltzmann equations for conduction band electrons and phonons, including nonlinear carrier excitation and relaxation processes as well as defect formation. The observed fast sub-100-femtosecond decay is shown to be caused by the interaction of non-equilibrium electrons with phonons and is in qualitative agreement with the results of the computer simulation. The observed sign reversal of the real part of the dielectric function from negative to positive after several hundred femtoseconds is attributed to the formation of self-trapped excitons (STE's) in the forbidden bandgap. Both real and imaginary part of the dielectric function are successfully modeled with the Boltzmann equation when defect formation is included. The simulations show that STE formation leads to efficient, non-thermal excitation of phonon modes on a sub-picosecond time scale.

Zeller, Joachim; Sabbah, Ali J.; Mero, Mark; Alsing, Paul M.; McIver, John; Rudolph, Wolfgang G.

2004-06-01

343

Ultra-thin titanium oxide  

NASA Astrophysics Data System (ADS)

We demonstrate the fabrication of ultra-thin titanium oxide films by plasma-induced surface oxidation. Ellipsometry measurements indicate an oxide thickness of about 2 nm. Electrical characterization was performed on microscale and nanoscale metal-insulator-metal tunneling diodes. Electrical fields up to 22 MV/cm were applied without destroying the titanium oxide films. The current-voltage-characteristic of the diodes are found to be asymmetric with respect to zero bias when employing electrodes with different work functions. The permittivity of the ultra-thin titanium oxide was determined to be less than 6, which is the smallest permittivity that has been reported for titanium oxide.

Bareiß, M.; Kälblein, D.; Jirauschek, C.; Exner, A.; Pavlichenko, I.; Lotsch, B.; Zschieschang, U.; Klauk, H.; Scarpa, G.; Fabel, B.; Porod, W.; Lugli, P.

2012-08-01

344

Dielectric function of warm dense gold  

SciTech Connect

Single-state measurements of the broadband (450-800 nm) dielectric function of gold using a supercontinuum probe are reviewed. These measurements have demonstrated the first evidence of the existence of band structure in ultrathin gold foils isochorically heated by a femtosecond laser pulse to energy densities of 10{sup 6}-10{sup 7} J/kg. The Drude component of the dielectric function increases with energy density while the interband component shows both enhancement and redshift. Ab initio molecular-dynamics calculations based on thermalized electrons cannot reproduce the experimental results, suggesting a non-Fermi distribution of excited electrons.

Ping, Y.; Ogitsu, T.; Schwegler, E.; Collins, G. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Hanson, D.; Koslow, I. [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia (Canada); Prendergast, D. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Ng, A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia (Canada)

2008-05-15

345

Principles of perfect and ultrathin anti-reflection with applications to transparent electrode  

NASA Astrophysics Data System (ADS)

Anti-reflection(AR), a well-known technique of reducing unwanted reflections by applying an impedance matching layer, works for a specific wavelength and require the coating layer to be a quarter wavelength thick. A broadband operation of AR, however, is not fully understood except for the trial and error method. Here, we present a systematic analytic method of AR without the restriction of wavelength or thickness, i.e. achieving a perfect AR. Specifically, we find analytic permittivity and permeability profiles that remove any given impedance mismatch at the interface between two different dielectrics in a frequency independent way. Ultra-thin AR coating is also shown to be possible and confirmed experimentally with the l/25-wavelength thick AR coating layer made of metamaterials. We apply the concept of ultrathin double layer AR to the transparent conducting electrode, which we demonstrate by fabricating a low reflective dielectric/metal-layered electrode that provides significant electrical conductivity and light transparency.

Kim, Kyoung-Ho; Park, Q.-Han

2014-03-01

346

Characterization of Al2O3-HfO2-Al2O3 sandwiched MIM capacitor under DC and AC stresses  

NASA Astrophysics Data System (ADS)

In this paper, electrical properties and reliability of high capacitance density Metal-Insulator-Metal (MIM) capacitor with sandwiched hafnium-based dielectric is analyzed using three kinds of voltage stress; constant voltage stress (CVS), unipolar voltage and bipolar voltage stresses. The fabricated MIM capacitor shows not only high capacitance density but also low leakage current density of about ˜10 nA/cm2 at room temperature and 1 V. The relative variation of capacitance (?C/C0) increases and the variation of voltage linearity (?/?0) gradually decreases with stress-time due to the charge trapping effect in the high-k dielectric. The relative variations of capacitance and voltage linearity show the greater change by the bipolar voltage stress than CVS and unipolar voltage stresses.

Kwak, Ho-Young; Kwon, Hyuk-Min; Jung, Yi-Jung; Kwon, Sung-Kyu; Jang, Jae-Hyung; Choi, Woon-Il; Ha, Man-Lyun; Lee, Ju-Il; Lee, Song-Jae; Lee, Hi-Deok

2013-01-01

347

Near-field effect in classical optics of ultra-thin films  

Microsoft Academic Search

On the basis of a microscopic approach which employs integro-differential equations for local electromagnetic field strength, we have solved the boundary-value problem of linear classical optics for the reflection and transmittance of a light wave by an ultra-thin dielectric film. The consideration of discrete structure of the medium is shown to lead to a near-field effect. The essence of this

K. V. Krutitsky; S. V. Suhov

1997-01-01

348

Ultraviolet to near infrared response of optically sensitive nonvolatile memories based on platinum nano-particles and high-k dielectrics on a silicon on insulator substrate  

NASA Astrophysics Data System (ADS)

An optically triggered nonvolatile memory based on platinum nano-particles embedded within a SiO2 and HfO2 dielectric stack on a silicon on insulator (SOI) substrate is presented. The memory cell exhibits a very wide spectral response, from 220 nm to 950 nm much wider than common photo-detectors fabricated on SOI. It offers several functionalities including a low programming voltage and wide hysteresis of the capacitance-voltage characteristics, an illumination and voltage sweep amplitude dependent hysteresis of the current-voltage characteristics, and plasmonic enhanced, efficient broad-band photo detection.

Mikhelashvili, V.; Meyler, B.; Shneider, Y.; Yofis, S.; Salzman, J.; Atiya, G.; Cohen-Hyams, T.; Ankonina, G.; Kaplan, W. D.; Lisiansky, M.; Roizin, Y.; Eisenstein, G.

2013-02-01

349

Sub1.3 nm Amorphous Tantalum Pentoxide Gate Dielectrics for Damascene Metal Gate Transistors  

Microsoft Academic Search

The formation process of amorphous tantalum pentoxide (Ta2O5) gate dielectrics was developed for sub-0.1 mum damascene metal gate transistors. Ta2O5 film deposition at high temperature (550°C) on ultrathin (1 nm) oxynitride interface layer improves the surface morphology and decreases the carbon contamination in films. Elimination of post-deposition annealing suppresses the increase of interface layer thickness, and hence, ultrathin equivalent oxide

Seiji Inumiya; Atsushi Yagishita; Tomohiro Saito; Masaki Hotta; Yoshio Ozawa; Kyoichi Suguro; Yoshitaka Tsunashima; Tsunetoshi Arikado

2000-01-01

350

Intercalative poly(carbazole) precursor electropolymerization within hybrid nanostructured titanium oxide ultrathin films.  

PubMed

A protocol for nanostructuring and electropolymerization of a hybrid semiconductor polycarbazole-titanium oxide ultrathin film is described. Ultrathin (<100 nm) films based on polycarbazole precursor polyelectrolytes and titanium oxide (TiOx) have been fabricated by combining the layer-by-layer (LbL) and surface sol-gel layering techniques. Film growth was followed and confirmed through UV-vis spectroscopy, ellipsometry and quartz crystal microbalance with dissipation (QCM-D). Subsequent anodic electrochemical oxidation of the carbazole pendant units afforded a conjugated polymer network (CPN) film within intercalating TiOx layers of cross-linked and ?-conjugated carbazole units. Cyclic voltammetry (CV), UV-vis, and fluorescence spectroscopy measurements confirmed this process. The LbL-driven polyelectrolyte deposition process resulted in a quantified electrochemical response, proportional to the number of layers, while the TiOx acted as a dielectric spacer limiting electron transfer kinetics and attenuating energy transfer in fluorescence. Electro-optical properties were compared with other polycarbazole thin film materials with respect to bandgap energy (Eg). The straightforward protocol in film nanostructuring and barrier/dielectric properties of the inorganic oxide slab (denoted here as, TiOx) should enable applications in organic light-emitting diodes (OLEDs), dielectric mirrors, planar waveguides, and photovoltaic devices for these hybrid ultrathin films. PMID:21080659

Frau, Antonio F; Estillore, Nicel C; Fulghum, Timothy M; Advincula, Rigoberto C

2010-12-01

351

Trapping of hydrogen in hafnium-based high kappa dielectric thin films for advanced CMOS applications  

NASA Astrophysics Data System (ADS)

In recent years, advanced high kappa gate dielectrics are under serious consideration to replace SiO2 and SiON in semiconductor industry. Hafnium-based dielectrics such as hafnium oxides, oxynitrides and Hf-based silicates/nitrided silicates are emerging as some of the most promising alternatives to SiO2/SiON gate dielectrics in complementary metal oxide semiconductor (CMOS) devices. Extensive efforts have been taken to understand the effects of hydrogen impurities in semiconductors and its behavior such as incorporation, diffusion, trapping and release with the aim of controlling and using it to optimize the performance of electronic device structures. In this dissertation, a systematic study of hydrogen trapping and the role of carbon impurities in various alternate gate dielectric candidates, HfO2/Si, HfxSi1-xO2/Si, HfON/Si and HfON(C)/Si is presented. It has been shown that processing of high kappa dielectrics may lead to some crystallization issues. Rutherford backscattering spectroscopy (RBS) for measuring oxygen deficiencies, elastic recoil detection analysis (ERDA) for quantifying hydrogen and nuclear reaction analysis (NRA) for quantifying carbon, X-ray diffraction (XRD) for measuring degree of crystallinity and X-ray photoelectron spectroscopy (XPS) were used to characterize these thin dielectric materials. ERDA data are used to characterize the evolution of hydrogen during annealing in hydrogen ambient in combination with preprocessing in oxygen and nitrogen.

Ukirde, Vaishali

352

Magnetism in ultrathin film structures  

NASA Astrophysics Data System (ADS)

In this paper, we review some of the key concepts in ultrathin film magnetism which underpin nanomagnetism. We survey the results of recent experimental and theoretical studies of well characterized epitaxial structures based on Fe, Co and Ni to illustrate how intrinsic fundamental properties such as the magnetic exchange interactions, magnetic moment and magnetic anisotropies change markedly in ultrathin films as compared with their bulk counterparts, and to emphasize the role of atomic scale structure, strain and crystallinity in determining the magnetic properties. After introducing the key length scales in magnetism, we describe the 2D magnetic phase transition and survey studies of the thickness dependent Curie temperature and the critical exponents which characterize the paramagnetic-ferromagnetic phase transition. We next discuss recent experimental and theoretical results on the determination of the exchange constant, followed by an overview of measurements of the magnetic moment in the elemental 3d transition metal thin films in the various crystal phases that have been successfully stabilized, thereby illustrating the sensitivity of the magnetic moment to the local symmetry and to the atomic environment. Finally, we discuss briefly the magnetic anisotropies of Fe, Co and Ni in the fcc crystalline phase, to emphasize the role of structure and the details of the interface in influencing the magnetic properties. The dramatic effect that adsorbates can have on the magnetic anisotropies of thin magnetic films is also discussed. Our survey demonstrates that the fundamental properties, namely, the magnetic moment and magnetic anisotropies of ultrathin films have dramatically different behaviour compared with those of the bulk while the comparable size of the structural and magnetic contributions to the total energy of ultrathin structures results in an exquisitely sensitive dependence of the magnetic properties on the film structure.

Vaz, C. A. F.; Bland, J. A. C.; Lauhoff, G.

2008-05-01

353

Non-linear dielectric constant increase with Ti composition in high-k ALD-HfTiOx films after O2 crystallization annealing  

NASA Astrophysics Data System (ADS)

HfTiOx films deposited on TiN, Pt and Al2O3/Si bottom electrodes (BE) by Atomic Layer Deposition (ALD) method were investigated in terms of the crystallization temperature, dielectric constant and leakage current. The as-deposited films show a linear increase of dielectric constant from 20 (HfO2) to 40 (TiO2) as a function of Ti content in the film. On the other hands, the dielectric constant of HfTiOx films with 64% - 30% Hf content increases up to 60 after crystallization annealing, which strongly correlates with the appearance of the orthorhombic HfTiO4 structure. Furthermore, the thermal treatment in O2 ambient is found to have a drastic effect to decrease the leakage current density (Jg). As a result, 10-8 A/cm2 at Vg = +1V with 0.8nm EOT is achieved with 30%-Hf contained film.

Tomida, K.; Popovici, M.; Opsomer, K.; Menou, N.; Wang, W. C.; Delabie, A.; Swerts, J.; Steenbergen, J.; Kaczer, B.; Elshocht, S. V.; Detavernier, C.; Afanas'ev, V. V.; Wouters, D. J.; Kittl, J. A.

2010-02-01

354

High-yield of memory elements from carbon nanotube field-effect transistors with atomic layer deposited gate dielectric  

NASA Astrophysics Data System (ADS)

Carbon nanotube field-effect transistors (CNT FETs) have been proposed as possible building blocks for future nano-electronics. But a challenge with CNT FETs is that they appear to randomly display varying amounts of hysteresis in their transfer characteristics. The hysteresis is often attributed to charge trapping in the dielectric layer between the nanotube and the gate. We find that the memory effect can be controlled by carefully designing the gate dielectric in nm-thin layers. By using atomic layer depositions (ALD) of HfO2 and TiO2 in a triple-layer configuration, we achieve to our knowledge the first CNT FETs with consistent and narrowly distributed memory effects in their transfer characteristics. The study includes 94 CNT FET samples, providing a good basis for statistics on the hysteresis seen in five different CNT-gate configurations.

Rinkiö, Marcus; Johansson, Andreas; Zavodchikova, Marina Y.; Jussi Toppari, J.; Nasibulin, Albert G.; Kauppinen, Esko I.; Törmä, Päivi

2008-10-01

355

Reliability characterizations and failure mechanism of ultra-thin oxides for MOS devices  

NASA Astrophysics Data System (ADS)

The aggressive scaling of smaller/faster logic and memory devices demands accurate reliability characterization and knowledge of the failure mechanisms of ultra-thin (<30 A) silicon dioxide (SiO 2) layers in the gates of metal-oxide semiconductor (MOS) structures. The increased occurrence of soft breakdown in ultra-thin oxide films necessitates the development of more sophisticated techniques to detect breakdown. One such technique is by interrupting stress and monitoring stress-induced leakage current (SILC) or interface state density (Dit). The effect of interrupting stress was carefully studied and determined not to affect device lifetime. A comprehensive time-dependent dielectric breakdown (TDDB) study was conducted on ultra-thin oxide over a temperature ranging from 220°C to 350°C to study temperature acceleration. The results of the study showed that both hard and soft breakdown modes exhibit the same temperature dependence. The choice of a failure model for time/charge to breakdown (tBD /QBD) is critical for accurate reliability extrapolation. In this work, two more experiments were carried out to clarify the current physical mechanisms responsible to dielectric wear-out. The first experiment investigated the effects of pulsed biased stress on device lifetime. A lifetime enhancement under bipolar pulse stress was observed. The results suggest that previously proposed mechanism of hole de-trapping in thick oxide may not be responsible for the lifetime increase observed here for ultra-thin oxides. The second experiment studied the effects of heavy ion on the reliability of ultra-thin SiO2. Annealing and electron injection experiments on irradiated devices with heavy ion implied that holes were significantly created and trapped inside SiO2 without causing the SiO2 to breakdown. The results from these two studies suggest that breakdown of ultra-thin oxides is not caused by holes and that the anode hole injection (AHI) model for constant voltage stress (CVS) is unwarranted in the ultra-thin regime.

Wang, Bin

356

Carrier conduction in ultrathin nitrided oxide films  

Microsoft Academic Search

Electrical conduction in ultrathin nitrided oxide films on silicon has been investigated by comparing it with that in ultrathin oxide. Significant current enhancement in the nitrided oxide and partial recovery of the enhancement by O2 annealing were observed, which can be satisfactorily explained by a two-step tunneling via traps generated in the nitrided oxide during nitridation. From the comparison between

Eiichi Suzuki; Dieter K. Schroder; Yutaka Hayashi

1986-01-01

357

Substrate dielectric effects on graphene field effect transistors  

NASA Astrophysics Data System (ADS)

Graphene is emerging as a promising material for future electronics and optoelectronics applications due to its unique electronic structure. Understanding the graphene-dielectric interaction is of vital importance for the development of graphene field effect transistors (FETs) and other novel graphene devices. Here, we extend the exploration of substrate dielectrics from conventionally used thermally grown SiO2 and hexagonal boron nitride films to technologically relevant deposited dielectrics used in semiconductor industry. A systematic analysis of morphology and optical and electrical properties was performed to study the effects of different substrates (SiO2, HfO2, Al2O3, tetraethyl orthosilicate (TEOS)-oxide, and Si3N4) on the carrier transport of chemical vapor deposition-derived graphene FET devices. As baseline, we use graphene FETs fabricated on thermal SiO2 with a relatively high carrier mobility of 10 000 cm2/(V s). Among the deposited dielectrics studied, silicon nitride showed the highest mobility, comparable to the properties of graphene fabricated on thermal SiO2. We conclude that this result comes from lower long range scattering and short range scattering rates in the nitride compared those in the other deposited films. The carrier fluctuation caused by substrates, however, seems to be the main contributing factor for mobility degradation, as a universal mobility-disorder density product is observed for all the dielectrics examined. The extrinsic doping trend is further confirmed by Raman spectra. We also provide, for the first time, correlation between the intensity ratio of G peak and 2D peak in the Raman spectra to the carrier mobility of graphene for different substrates.

Hu, Zhaoying; Prasad Sinha, Dhiraj; Ung Lee, Ji; Liehr, Michael

2014-05-01

358

Electron tunneling through ultrathin boron nitride crystalline barriers.  

PubMed

We investigate the electronic properties of ultrathin hexagonal boron nitride (h-BN) crystalline layers with different conducting materials (graphite, graphene, and gold) on either side of the barrier layer. The tunnel current depends exponentially on the number of h-BN atomic layers, down to a monolayer thickness. Conductive atomic force microscopy scans across h-BN terraces of different thickness reveal a high level of uniformity in the tunnel current. Our results demonstrate that atomically thin h-BN acts as a defect-free dielectric with a high breakdown field. It offers great potential for applications in tunnel devices and in field-effect transistors with a high carrier density in the conducting channel. PMID:22380756

Britnell, Liam; Gorbachev, Roman V; Jalil, Rashid; Belle, Branson D; Schedin, Fred; Katsnelson, Mikhail I; Eaves, Laurence; Morozov, Sergey V; Mayorov, Alexander S; Peres, Nuno M R; Neto, Antonio H Castro; Leist, Jon; Geim, Andre K; Ponomarenko, Leonid A; Novoselov, Kostya S

2012-03-14

359

Optical transmission through subwavelength hole arrays in ultrathin metal films  

NASA Astrophysics Data System (ADS)

Contrary to thick opaque metal films, where an extraordinary high transmission of light is observed through subwavelength hole arrays, in ultrathin metal films perforation can lead to a suppressed or an enhanced transmission. Here we systematically investigate the optical transmission through semitransparent Au films structured with square arrays of subwavelength holes experimentally and theoretically. We measure the transmission at various angles of incidence through hole arrays with different thicknesses, diameters, and periodicities. We compare the data with an empty lattice approximation and with calculations based on a Fourier modal method. The results evidence that for gold the exact dielectric function has to be considered and that not only the periodicity and film thickness influences the transmission, but that also the shape and diameter of the holes play an important role.

Braun, Julia; Gompf, Bruno; Weiss, Thomas; Giessen, Harald; Dressel, Martin; Hübner, Uwe

2011-10-01

360

Topographic measurements of supersmooth dielectric films made with a mechanical profiler and a scanning force microscope  

NASA Astrophysics Data System (ADS)

The roughnesses of five supersmooth dielectric films of Si3N4, TiO2 , HfO2, Ta2O5 , and Al2O3 prepared by an ion-beam-sputtering technique were measured with a commercial Talystep mechanical profiler and a sensitive Leica WYKO SPM30 scanning force microscope (SFM) to determine how much roughness the films added to the approximately 1-A-rms roughness fused-silica substrates on which they were deposited. In all cases the increase in roughness for the three-quarter-wave optical thickness films was a small fraction of an angstrom. SFM measurements showed that the topography of the Ta2O5 and Al2O3 films was less random than that of the other film materials and the substrates.

Bennett, Jean M.; Tehrani, Mohammad M.; Jahanmir, Jay; Podlesny, John C.; Balter, Tami L.

1995-01-01

361

Detection of Dielectric Trap States in Hafnium Oxide By Single Electron Tunneling Force Spectroscopy  

NASA Astrophysics Data System (ADS)

Atomic scale detection and imaging of electronic trap states in dielectric films has recently been demonstrated.ootnotetextJ.P. Johnson et al, Nanotechnology 20 (2009) 055701 Standard methods typically provide characterization over a much larger scale. Single Electron Tunneling Force Spectroscopy has been employed to measure the energy levels of trap states in HfO2 with sub-nanometer spatial resolution. Analysis of individual spectra obtained at different locations shows variation in the density of defect states. When multiple spectra taken from 40 different locations are averaged, a broad peak 0.3 eV below the conduction band is observed, which agrees with data obtained over large areas by standard measurements.ootnotetextG. Ribes et al, IEEE Trans. Dev. Mat. Reliability 6, 132 (2006). Additional peaks, not seen by the standard methods, are also observed. The method will be described and the data discussed.

Winslow, Dustin; Johnson, Jon; Williams, Clayton

2011-03-01

362

Increase of the damage thresholds of dielectric layer systems for the Nd laser  

NASA Astrophysics Data System (ADS)

High power layer systems were developed and optimized using the electron beam vapor deposition technique, with emphasis on the determination of the parameters which influence the interaction between dielectric layers and intense layer radiation. The measurement of these quantities allowed a theoretically well-founded classification of the damage mechanism in single layers of TiO2, Ta2O5, HfO2, ZrO2, AL2O3, and SiO2. The transition in layer systems are shown to contribute essentially to the damage process. The optimization of antireflection coatings and highly reflecting mirrors for gradual systems increase the damage threshold by 20 percent in comparison with conventional designs up to 50j/sq cm. Ninety-degree phase-active mirrors were designed and realized with a damage threshold up to 30j/sq cm.

Ristau, Detlev

363

On the damage behavior of dielectric films when illuminated with multiple femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

The physical effects reducing the damage threshold of dielectric films when exposed to multiple femtosecond pulses are investigated. The measured temperature increase of a Ta2O5 film scales exponentially with the pulse fluence. A polarized luminescence signal is observed that depends quadratically on the pulse fluence and is attributed to two-photon excitation of self-trapped excitons that form after band-to-band excitation. The damage fluence decreases with increasing pulse number, but is independent of the repetition rate from 1 Hz to 1 kHz at a constant pulse number. The repetition rate dependence of the breakdown threshold is also measured for TiO2, HfO2, Al2O3, and SiO2 films. A theoretical model is presented that explains these findings.

Mero, Mark; Clapp, Benjamin R.; Jasapara, Jayesh C.; Rudolph, Wolfgang G.; Ristau, Detlev; Starke, Kai; Krüger, Jörg; Martin, Sven; Kautek, Wolfgang

2005-05-01

364

Technological development of high-k dielectric FinFETs for liquid environment  

NASA Astrophysics Data System (ADS)

This work presents the technological development and characterization of n-channel fully depleted high-k dielectric FinFETs (Fin Field Effect Transistor) for applications in a liquid environment. Herein, we provide a systematic approach based on Finite Element Analysis for a high-control fabrication process of vertical Si-fins on bulk and we provide many useful fabrication expedients. Metal gate FinFETs have been successfully electrically characterized, showing excellent subthreshold slope SS = 72 mV/dec and high Ion/Ioff ? 106 ratio, with power consumption of the order of tens of nW. The FinFETs have also been proved to correctly behave in a liquid environment. We also present the HfO2 characterization towards full pH response sensing applications.

Rigante, S.; Scarbolo, P.; Bouvet, D.; Wipf, M.; Bedner, K.; Ionescu, A. M.

2014-08-01

365

Characterization of defect evolution in ultrathin SiO2 layers under applied electrical stress  

NASA Astrophysics Data System (ADS)

The structural evolution of ultrathin dielectric SiO2 layers within a Co-silicide/poly-Si/SiO2/Si multilayer system was studied by in situ transmission electron microscopy (TEM). The interface structure represents a model system for field effect transistors with a SiO2 dielectric layer. Electrical bias was applied across the interfaces of cross sectional TEM samples using a scanning tunneling microscopy (STM) tip. Atomic structure modifications of the dielectric layer due to the applied electrical field were observed by this in situ STM-TEM technique. Constant bias (+5.0 V) and ramped bias (+3.0 to +10.5 V) stresses applied to the CoSi2 gate electrode resulted in a loss in capacitance of the dielectric layer consistent with descriptions of soft dielectric breakdown (SBD) and hard dielectric breakdown (HBD). It was found that SBD events are characterized by fluctuations within uniform current step increase of 21 nA and increased roughness of the SiO2 film due to oxygen vacancy percolation. HBD, however, was found to be preceded by multiple SBD events between +6.5 V and +10 V, cobalt atom migration into the dielectric layer, partial crystallization of the amorphous gate dielectric (dielectric breakdown induced epitaxy), and significant diffusion of oxygen from the SiO2 layer into the silicon substrate through a reduction-oxidation reaction of the Si/SiO2 interface. Experimental results demonstrate the feasibility of in situ STM-TEM experiments for studying time-dependent dielectric breakdown behaviors to obtain a direct correlation of individual defect structures and their corresponding electrical signatures. Experimental limitations of this new technique are critically discussed.

Bonifacio, Cecile S.; van Benthem, Klaus

2012-11-01

366

Low-temperature deposition of ultrathin SiO2 films on Si substrates  

NASA Astrophysics Data System (ADS)

We present a detailed investigation of the properties of silicon dioxide deposited at a low temperature. The advantages of this process include its low thermal requirements (about 200 °C), the absence of corrosive by-products and the lack of need of vacuum equipment. Sol solutions were prepared for the deposition of ultrathin SiO2 films by spin-coating at the low annealing temperature of 200 °C. The layers' thickness was 24 nm and 5 nm. We describe in detail the material properties of this novel low-temperature SiO2 layers obtained by extensive characterization using Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), XPS spectroscopy, capacitance-voltage (C-V) and current-voltage (I-V) measurements. The ultrathin oxide layers on Si substrates show good dielectric properties.

Vitanov, P.; Harizanova, A.; Ivanova, T.; Dikov, H.

2014-05-01

367

Ultrathin Si capping layer suppresses charge trapping in HfOxNy\\/Ge metal-insulator-semiconductor capacitors  

Microsoft Academic Search

In this study the authors investigated the Ge outdiffusion characteristics of HfOxNy\\/Ge metal-insulator-semiconductor capacitors to determine their charge trapping behavior. Capping the Ge substrate with an ultrathin Si layer inhibits the incorporation of Ge into the high-k bulk dielectric in the form of GeOx, thereby diminishing the resultant oxide charge trapping. The thermal stability of the entire capacitor structure was

Chao-Ching Cheng; Chao-Hsin Chien; Guang-Li Luo; Chun-Hui Yang; Mei-Ling Kuo; Je-Hung Lin; Chun-Yen Chang

2007-01-01

368

Effect of Cr additions on the electrical properties of Ni–BaTiO 3 ultra-thin multilayer capacitors  

Microsoft Academic Search

Multilayer ceramic capacitors based on BaTiO3 dielectric compositions and Ni inner electrodes have complex interfacial reactions that impact the continuity of the inner\\u000a electrode microstructure. Previously we demonstrated that through the addition of Cr to Ni, a significant improvement in the\\u000a continuity of ultra-thin Ni electrodes in Ni–BaTiO3 multilayer capacitors could be achieved. Here, the effect of the Cr addition

Anton V. Polotai; Tae-Hee Jeong; Gai-Ying Yang; Elizabeth C. Dickey; Clive A. Randall; Pascal Pinceloup; Abhijit S. Gurav

2009-01-01

369

Ultrathin Si capping layer suppresses charge trapping in HfOxNy/Ge metal-insulator-semiconductor capacitors  

NASA Astrophysics Data System (ADS)

In this study the authors investigated the Ge outdiffusion characteristics of HfOxNy/Ge metal-insulator-semiconductor capacitors to determine their charge trapping behavior. Capping the Ge substrate with an ultrathin Si layer inhibits the incorporation of Ge into the high-k bulk dielectric in the form of GeOx, thereby diminishing the resultant oxide charge trapping. The thermal stability of the entire capacitor structure was also improved after performing an additional Si passivation process.

Cheng, Chao-Ching; Chien, Chao-Hsin; Luo, Guang-Li; Yang, Chun-Hui; Kuo, Mei-Ling; Lin, Je-Hung; Chang, Chun-Yen

2007-01-01

370

Dielectric gradient metasurface optical elements.  

PubMed

Gradient metasurfaces are two-dimensional optical elements capable of manipulating light by imparting local, space-variant phase changes on an incident electromagnetic wave. These surfaces have thus far been constructed from nanometallic optical antennas, and high diffraction efficiencies have been limited to operation in reflection mode. We describe the experimental realization and operation of dielectric gradient metasurface optical elements capable of also achieving high efficiencies in transmission mode in the visible spectrum. Ultrathin gratings, lenses, and axicons have been realized by patterning a 100-nanometer-thick Si layer into a dense arrangement of Si nanobeam antennas. The use of semiconductors can broaden the general applicability of gradient metasurfaces, as they offer facile integration with electronics and can be realized by mature semiconductor fabrication technologies. PMID:25035488

Lin, Dianmin; Fan, Pengyu; Hasman, Erez; Brongersma, Mark L

2014-07-18

371

Ultrathin, flexible organic-inorganic hybrid solar cells based on silicon nanowires and PEDOT:PSS.  

PubMed

Recently, free-standing, ultrathin, single-crystal silicon (c-Si) membranes have attracted considerable attention as a suitable material for low-cost, mechanically flexible electronics. In this paper, we report a promising ultrathin, flexible, hybrid solar cell based on silicon nanowire (SiNW) arrays and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The free-standing, ultrathin c-Si membranes of different thicknesses were produced by KOH etching of double-side-polished silicon wafers for various etching times. The processed free-standing silicon membranes were observed to be mechanically flexible, and in spite of their relatively small thickness, the samples tolerated the different steps of solar cell fabrication, including surface nanotexturization, spin-casting, dielectric film deposition, and metallization. However, in terms of the optical performance, ultrathin c-Si membranes suffer from noticeable transmission losses, especially in the long-wavelength region. We describe the experimental performance of a promising light-trapping scheme in the aforementioned ultrathin c-Si membranes of thicknesses as small as 5.7 ?m employing front-surface random SiNW texturization in combination with a back-surface distribution of silver (Ag) nanoparticles (NPs). We report the enhancement of both the short-circuit current density (JSC) and the open-circuit voltage (VOC) that has been achieved in the described devices. Such enhancement is attributable to the plasmonic backscattering effect of the back-surface Ag NPs, which led to an overall 10% increase in the power conversion efficiency (PCE) of the devices compared to similar structures without Ag NPs. A PCE in excess of 6.62% has been achieved in the described devices having a c-Si membrane of thickness 8.6 ?m. The described device technology could prove crucial in achieving an efficient, low-cost, mechanically flexible photovoltaic device in the near future. PMID:24568116

Sharma, Manisha; Pudasaini, Pushpa Raj; Ruiz-Zepeda, Francisco; Elam, David; Ayon, Arturo A

2014-03-26

372

Physicochemically functional ultrathin films by interfacial polymerization  

DOEpatents

Interfacially-polymerized ultrathin films containing physicochemically functional groups are disclosed, both with and without supports. Various applications are disclsoed, including membrane electrodes, selective membranes and sorbents, biocompatible materials, targeted drug delivery, and narrow band optical absorbers.

Lonsdale, Harold K. (Bend, OR); Babcock, Walter C. (Bend, OR); Friensen, Dwayne T. (Bend, OR); Smith, Kelly L. (Bend, OR); Johnson, Bruce M. (Bend, OR); Wamser, Carl C. (West Linn, OR)

1990-01-01

373

Physicochemically functional ultrathin films by interfacial polymerization  

DOEpatents

Interfacially-polymerized ultrathin films containing physicochemically functional groups are disclosed, both with and without supports. Various applications are disclosed, including membrane electrodes, selective membranes and sorbents, biocompatible materials, targeted drug delivery, and narrow band optical absorbers. 3 figs.

Lonsdale, H.K.; Babcock, W.C.; Friensen, D.T.; Smith, K.L.; Johnson, B.M.; Wamser, C.C.

1990-08-14

374

Ultrathin films as photomechanical transducers  

NASA Technical Reports Server (NTRS)

In order to investigate the photomechanical effect in ultrathin films, several commercially available polymers of various structure and properties have been studied experimentally below the glass transition temperature. In the experiments using an Instron test machine equipped with a 200-g load cell and a microscope stage illuminator as the light source, the load at the fixed strain was recorded as a function of time. Plots of the steady-state change in stress as a function of the intensity of the incident radiation are presented for several of the materials studied. The response is found to be linear; the greater the intensity of the incident radiation, the greater is the change in stress.

Sarbolouki, M. N.; Fedors, R. F.

1979-01-01

375

Anisotropic permittivity of ultra-thin crystalline Au films: Impacts on the plasmonic response of metasurfaces  

NASA Astrophysics Data System (ADS)

It has been determined by density functional theory (DFT) simulations that the extracted permittivities of ultra-thin crystalline gold (Au) films exhibit large anisotropies which are not predicted by classical models or previous experimental determinations of the dielectric function. The optical scattering characteristics of a periodic array of Au discs are simulated with the DFT extracted permittivity and contrasted against those obtained with several commonly used Au permittivity models. It is demonstrated that the DFT-based transmittance spectra for these plasmonic metasurfaces lead to significantly redshifted results when compared to those predicted by standard Drude and Johnson-Christy permittivity models.

Campbell, Sawyer D.; Ziolkowski, Richard W.; Cao, Jiangrong; Laref, Slimane; Muralidharan, Krishna; Deymier, Pierre

2013-08-01

376

Chemical control over the formation and reactivity of ultra-thin films and amino-terminated layers on silicon  

NASA Astrophysics Data System (ADS)

The physical-chemical properties of several interfacial systems of technological relevance are investigated, having as a common goal the elucidation of strategies towards their atomic- and molecular-level control. Such systems can be classified in three groups: (i) ultra-thin films deposited using metalorganic precursors, (ii) metalorganic monolayers on silicon, and (iii) amine-functionalized silicon surfaces. Experimental, theoretical and chemometric methods are conveniently combined to gain a solid understanding of these systems. The ultra-thin films under investigation are titanium carbonitride (TiNC) and hafnium oxide (HfO2). Since these films may serve as substrates for deposition of other materials in circuit components, their surface chemistry needs to be understood and controlled in order to facilitate further deposition steps. The surface of a TiCN film is transformed to titanium nitride (TiN) through nitridation with ammonia; this compositional change can be reversed by the partial decomposition of ethylene molecules on the surface. The surface reactivity is observed to depend on the film composition, and therefore the method described above serves to reversibly tune the reactivity of Ti-based films. As for HfO2 films, it is found that the deposition temperature affects the degree of crystallinity of the films, which in turn affects their surface chemistry. Thus, together with a control of the composition, it is found that the reactivity of a film can be controlled precisely by controlling the crystallinity. The investigation of metalorganic monolayers on silicon surfaces was motivated by the need for understanding the first steps of metalorganic-based deposition of films, which is usually characterized by a heavy presence of contaminants that degrade the film properties. Through a combination of vibrational (infrared) spectroscopy and theoretical methods, a feasible pathway for the adsorption and decomposition of Ti[N(CH3)2]4 is found. This pathway starts with the ligand-mediated attachment of the precursor (through a N atom), followed by dissociation of a metal-ligand bond. In addition, the C-H bond is broken, possibly forming Si-C bonds and causing carbon incorporation. This model is found to be rather robust and to adequately describe other types of metalorganic precursors. It allows establishing a generalized model able to explain the success or failure of a metalorganic precursor chemistry for film deposition. Finally, amine-functionalized silicon surfaces are considered as prototypical systems where the spatial distribution of adsorbates and the control over the reactivity of surface sites can be investigated. The spatial distribution of molecules is investigated at the atomic level by considering the saturation of a Si(100) surface with NH3. It is found that the distribution of (Si)NH2 species can be controlled thermally and, more importantly, that during thermal decomposition N inserts into the substrate in manners that minimize the arising strain. When the surface is covered with NH 3 or with organic amines, its chemical behavior is determined by the basicity of the molecule functionalizing the surface. The precise tuning of the reactivity (basicity) of surface sites opens the doors for highly controllable, selective reactions. Although these results are obtained from rather fundamental grounds, their interpretation is often translated into manners in which technological applications can be improved. Further directions worth exploring emanated from this work are outlined and discussed. Ultimately, this work intends to highlight the current importance of surface physical chemistry in the continuous development of modern society through the improvement of its technology.

Rodriguez-Reyes, Juan Carlos F.

377

Electrical characterization and process control of cost-effective high-k aluminum oxide gate dielectrics prepared by anodization followed by furnace annealing  

Microsoft Academic Search

A cost-effective technique was introduced to prepare ultrathin aluminum oxide (Al2O3) gate dielectrics with equivalent oxide thickness (EOT) down to 14 Å. Al2O3 was fabricated by anodic oxidation (anodization) of ultrathin Al films at room temperature in deionized water and then furnace annealed at 650°C in N2 ambient. Both dc and dac (dc superimposed with ac) anodization techniques were investigated.

Szu-Wei Huang; Jenn-Gwo Hwu

2003-01-01

378

Electrical, optical and micro-structural properties of ultra-thin HfTiON films  

NASA Astrophysics Data System (ADS)

Nitrogen is incorporated with different contents into ultra-thin HfTiO dielectric films deposited on Si (1 0 0) substrate by radio frequency (RF) magnetron sputtering under a N2 atmosphere. The improved thermal stability and surface microstructure are demonstrated by X-ray diffraction (XRD) and atomic force microscope (AFM) due to the incorporation of nitrogen. The optical characterization of the ultra-thin HfTiON films exhibits a large band gap attributed to nitrogen doping, and a reduction in band gap with increase of N-doped concentration. More importantly, electrical properties of ultra-thin HfTiON films related to different nitrogen-incorporated content are systematically investigated. The N-doped content of HfTiON films deposited under Ar/N2 flow ratio of 30/15 (sccm) has been proved to be an optimal amount, based on which HfTiON films through 500 °C rapid thermal annealing (RTA) treatment further achieve the most favorably excellent electrical properties in terms of a lower gate leakage current density of 7.72 × 10-6 A/cm2 and a higher permittivity of 35.31. Moreover, the dominant conduction mechanisms of Pt/HfTiON/p-Si structures for both as-deposited and annealed HfTiON films are discussed by data fitting method in details.

Zhang, Jieqiong; Li, Zhixiong; Zhou, Hai; Ye, Cong; Wang, Hao

2014-03-01

379

Silicon nanowires with high-k hafnium oxide dielectrics for sensitive detection of small nucleic acid oligomers.  

PubMed

Nanobiosensors based on silicon nanowire field effect transistors offer advantages of low cost, label-free detection, and potential for massive parallelization. As a result, these sensors have often been suggested as an attractive option for applications in point-of-care (POC) medical diagnostics. Unfortunately, a number of performance issues, such as gate leakage and current instability due to fluid contact, have prevented widespread adoption of the technology for routine use. High-k dielectrics, such as hafnium oxide (HfO(2)), have the known ability to address these challenges by passivating the exposed surfaces against destabilizing concerns of ion transport. With these fundamental stability issues addressed, a promising target for POC diagnostics and SiNWFETs has been small oligonucleotides, more specifically, microRNA (miRNA). MicroRNAs are small RNA oligonucleotides which bind to mRNAs, causing translational repression of proteins, gene silencing, and expressions are typically altered in several forms of cancer. In this paper, we describe a process for fabricating stable HfO(2) dielectric-based silicon nanowires for biosensing applications. Here we demonstrate sensing of single-stranded DNA analogues to their microRNA cousins using miR-10b and miR-21 as templates, both known to be upregulated in breast cancer. We characterize the effect of surface functionalization on device performance using the miR-10b DNA analogue as the target sequence and different molecular weight poly-l-lysine as the functionalization layer. By optimizing the surface functionalization and fabrication protocol, we were able to achieve <100 fM detection levels of the miR-10b DNA analogue, with a theoretical limit of detection of 1 fM. Moreover, the noncomplementary DNA target strand, based on miR-21, showed very little response, indicating a highly sensitive and highly selective biosensing platform. PMID:22695179

Dorvel, Brian R; Reddy, Bobby; Go, Jonghyun; Duarte Guevara, Carlos; Salm, Eric; Alam, Muhammad Ashraful; Bashir, Rashid

2012-07-24

380

Silicon Nanowires with High-k Hafnium Oxide Dielectrics for Sensitive Detection of Small Nucleic Acid Oligomers  

PubMed Central

Nanobiosensors based on silicon nanowire field effect transistors offer advantages of low cost, label-free detection, and potential for massive parallelization. As a result, these sensors have often been suggested as an attractive option for applications in Point-of-care (POC) medical diagnostics. Unfortunately, a number of performance issues such as gate leakage and current instability due to fluid contact, have prevented widespread adoption of the technology for routine use. High-k dielectrics, such as hafnium oxide (HfO2), have the known ability to address these challenges by passivating the exposed surfaces against destabilizing concerns of ion transport. With these fundamental stability issues addressed, a promising target for POC diagnostics and SiNWFET’s has been small oligonucleotides, more specifically microRNA (miRNA). MicroRNA’s are small RNA oligonucleotides which bind to messenger RNA’s, causing translational repression of proteins, gene silencing, and expressions are typically altered in several forms of cancer. In this paper, we describe a process for fabricating stable HfO2 dielectric based silicon nanowires for biosensing applications. Here we demonstrate sensing of single stranded DNA analogues to their microRNA cousins using miR-10b and miR-21 as templates, both known to be upregulated in breast cancer. We characterize the effect of surface functionalization on device performance using the miR-10b DNA analogue as the target sequence and different molecular weight poly-l-lysine as the functionalization layer. By optimizing the surface functionalization and fabrication protocol, we were able to achieve <100fM detection levels of miR-10b DNA analogue, with a theoretical limit of detection of 1fM. Moreover, the non-complementary DNA target strand, based on miR-21, showed very little response, indicating a highly sensitive and highly selective biosensing platform.

Dorvel, Brian R.; Reddy, Bobby; Go, Jonghyun; Guevara, Carlos Duarte; Salm, Eric; Alam, Muhammad Ashraful; Bashir, Rashid

2012-01-01

381

Ultrathin, highly flexible and stretchable PLEDs  

NASA Astrophysics Data System (ADS)

We demonstrate ultrathin (2 µm thick) red and orange polymer light-emitting diodes with unprecedented mechanical properties in terms of their flexibility and ability to be stretched. The devices have a luminance greater than 100 cd m-2, sufficient for a variety of optoelectronic applications including indoor displays. They can be operated as free-standing ultrathin films, allowing for crumpling during device operation. Furthermore, they may be applied to almost any surface whether rigid or elastomeric, and can withstand the associated mechanical deformation. They are shown to be extremely flexible, with radii of curvature under 10 µm, and stretch-compatible to 100% tensile strain. Such ultrathin light-emitting foils constitute an important step towards integration with malleable materials like textiles and artificial skin.

White, Matthew S.; Kaltenbrunner, Martin; G?owacki, Eric D.; Gutnichenko, Kateryna; Kettlgruber, Gerald; Graz, Ingrid; Aazou, Safae; Ulbricht, Christoph; Egbe, Daniel A. M.; Miron, Matei C.; Major, Zoltan; Scharber, Markus C.; Sekitani, Tsuyoshi; Someya, Takao; Bauer, Siegfried; Sariciftci, Niyazi Serdar

2013-10-01

382

Dielectric Investigation of [(SrTiO3)6(BaTiO3)6]2 Multilayer Capacitor  

Microsoft Academic Search

Ferroelectric properties depend on the thickness of films. To observe the dielectric properties of ultrathin ferroelectric thin films, a [(SrTiO3)6(BaTiO3)6]2 multilayer thin film with a total thickness of 96 Å was investigated. X-ray diffraction confirmed that it was a well-epitaxial and highly strained film with a perovskite structure. The multilayer film exhibited ferroelectric behavior at room temperature and dielectric behavior

Yasuhiro Yoneda; Kiyoshi Sakaue; Hikaru Terauchi

2001-01-01

383

Dielectric Ceramics  

NASA Astrophysics Data System (ADS)

The structural and microwave properties of (Mg,Zn/Co)TiO3 dielectric ceramics have been investigated. The grown samples have been characterized by means of x-ray diffraction, Rietveld refinement, scanning electron microscopy, and energy dispersive x-ray spectroscopy analysis. The microwave dielectric properties of grown samples have been measured using the Hakki-Coleman resonator method and found to depend on the ionic polarizability, electronic polarizability, and Mg-site substitutions. The Mg0.95Zn0.05TiO3 compound shows a maximum Q × f value of 210,000 GHz (at 10 GHz), ?r of 16.31, and ?f value of -62.43.

Rajput, Shailendra Singh; Keshri, Sunita

2014-06-01

384

Increasing detectivity of polarization modulation infrared reflection-absorption spectroscopy for the study of ultrathin films deposited on various substrates.  

PubMed

In this paper, we present a simple way to increase the sensitivity of polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) for the study of ultrathin films deposited on dielectric and semiconductor substrates. The enhancement of the absorption band intensity is obtained by reducing the signal arising from the substrate. This is achieved by adding a polarizer after the sample in order to balance the polarized reflectivities of the sample. As a consequence, the contribution of the film to the PM-IRRAS signal is increased relative to that of the substrate. An enhancement factor of about 10 has been obtained for ultrathin organic films deposited on glass and spread at the air-water interface. This method has also allowed the study of the very thin native oxide layer present on silicon without the need for the reference spectrum of bare silicon. PMID:14639755

Saccani, J; Buffeteau, T; Desbat, B; Blaudez, D

2003-10-01

385

Low field leakage current and soft breakdown in ultra-thin gate oxides after heavy ions, electrons or X-ray irradiation  

Microsoft Academic Search

The excess leakage current across ultra-thin dielectrics has been studied for different ionizing radiation sources. Namely, X-rays, 8 MeV electrons, and three ion beams with different LETs values have been used on large area MOS capacitors with 4-nm thick oxides. Small oxide fields were applied during irradiation, reaching 3 MV\\/cm at most. For ionizing radiation with relatively low LET (<10

M. Ceschia; A. Paccagnella; S. Sandrin; G. Ghidini; J. Wyss; M. Lavale; O. Flament

1999-01-01

386

Ultrathin PDMS films: Microstructure and metastability  

Microsoft Academic Search

This dissertation focuses on ultra-thin liquid films, less than a few nanometers thick, of one polymer, polydimethylsiloxane (PDMS). PDMS, a model flexible linear polymer, also plays a very important role in many applications. There have been many speculations about the molecular conformation in these films; the very flexibility of the chains gives many possibilities. This dissertation will present experimental studies

Svetlana V. Primak

2002-01-01

387

Ultra-Thin Carbon Fiber Wire Saw.  

National Technical Information Service (NTIS)

Researchers focused on the development of an ultra-thin bonded abrasive wire saw which would make it possible to slice large ingots of expensive brittle materials such as Si, GaAs, Ge, SiO2, with minimum kerf losses and would reduce wafering process-induc...

G. L. Thompson P. J. Fordenbacher R. M. Washburn U. Ortabasi

1989-01-01

388

Ultrathin germanium-on-insulator tunneling field effect transistors  

NASA Astrophysics Data System (ADS)

As the CMOS downscaling is approaching its limits, there is greater need for alternative and unconventional devices to continue enhancing the performance of electronics. We report on the fabrication and electrical characterization of a CMOS-compatible germanium-on-insulator (GeOI) tunneling field effect transistor (TFET) device that can in principle switch more sharply than a standard FET. The source-drain current in the TFET is based on interband tunneling between an inversion channel and a counterdoped drain electrode. Taking advantage of the narrower bandgap of germanium, the devices are fabricated in ultra-thin GeOI and consist of a heavily p-type doped, epitaxially grown drain, an n-type ion-implanted source and a standard high-? dielectric gate stack with channel lengths down to 400 nm. The devices exhibit a reasonable on-off current ratio of more than 10^2 and improved on current compared to silicon-on-insulator TFETs. Current-voltage measurements at room and low temperatures will be presented to characterize the behavior of the fabricated transistors.

Kazazis, D.; Jannaty, P.; Zaslavsky, A.; Le Royer, C.; Tabone, C.; Clavelier, L.

2009-03-01

389

High k dielectrics on silicon: Effects of processing on nanostructure and properties  

NASA Astrophysics Data System (ADS)

High permittivity hafnia, HfO2, and hafnium silicate, HfSiO 4, are the most promising candidates to replace oxide (SiOx) or oxynitride (SiOxNy) based gate dielectrics in future generation CMOS devices. In this thesis, the effects of processing (deposition techniques, post deposition annealing, nitridation) on nanostructure evolution (crystallization, phase segregation, interlayer growth), changes in nanochemistry (impurity content, interfacial reaction, interdiffusion, oxygen diffusion, paramagnetic charge centers) and properties (EOT, oxide charges) of atomic layer deposited (ALD) Hf-O/Hf-Si-O films on Si, with different interlayers (IL), were studied. A variety of analytical techniques including XRD, RBS, XPS, SIMS, AFM, HRTEM, STEM-EELS and EPR were used. In general, PEALD Hf-O films deposited using metal-organic precursors showed a higher C and H and lower Cl content compared to thermal ALD films using halide based precursors. Also, as-deposited ALD films (Hf-O/IL/Si) showed the formation of Hf-O-Si bonds at the Hf-O/IL interface, with increasing tendency in the presence of a chemical oxide interlayer and upon oxygen annealing. Upon post deposition annealing (PDA) of ALD Hf-O films up to 1000°C, m-HfO2 was the stable crystalline phase. It was observed that the chemical oxide interlayer grew significantly during PDA in oxygen, the rate of which was a f (t, T) due to oxygen diffusion. Additionally, an annealed Hf-O stack (i.e., target Hf-O thickness of 4.0 nm/1.2 nm nitrided chemical oxide interlayer/Si) showed a chemically diffused HfSiOx region (2 nm) in between pure HfO2 (2 nm) and the interlayer (1.2 nm) as a result of interdiffusion and interfacial reactions. Therefore, a three-layer capacitor model was used to determine the respective contributions to the total EOT. Moreover, to correlate the presence of defects with density of interfacial states, as-deposited ALD Hf-O/chemical oxide IL/Si stacks were shown to be EPR active at 8K, due to Pb0, Pb1 type charge centers. Upon forming gas annealing (FGA) and PDA, these charge centers became hydrogen-passivated. Using remote plasma nitridation of an ALD Hf-O film on chemical oxide IL/Si, the Hf-O layer remained amorphous even at 1000°C and exhibited a reduced tendency towards Hf-O-Si bond formation and interlayer growth when nitrogen incorporation was ˜1.7 at % of surface Hf atoms. However, the positive fixed charge density increased and oxide trapped charge density decreased with nitrogen incorporation. Finally, upon PDA in nitrogen at 1000°C for 10 seconds of ALD Hf-Si-O films with 60 and 75 mol % HfO2, the amorphous films transformed to t-HfO2 nano-crystallites embedded in a silica-rich amorphous matrix. However, amorphous Hf-Si-O films with 40 mol% HfO2 (i.e., silica-rich) when subjected to the same PDA, phase segregated into predominantly two amorphous phases.

Das, Anirban

390

Investigation of MOS Interfaces with Atomic-Layer-Deposited High-k Gate Dielectrics on III-V Semiconductors  

NASA Astrophysics Data System (ADS)

The purpose of this research work was to investigate the surface passivation methods and metal gate/high-k dielectric gate stacks for metal-oxide-semiconductor devices (MOS) on III-V compound semiconductor materials -- (i) GaAs for future high-speed low-power logic devices and (ii) AlGaN/GaN heterostructure for future high-speed high-power devices. GaAs is a candidate material for high-mobility channel in a NMOS transistor to extend the CMOS scaling up to and beyond the 16-nm technology node. AlGaN/GaN heterostructure is useful in a MOS-high electron mobility transistor (MOS-HEMT) device for providing a high current-carrying two dimensional electron gas (2DEG) channel. The interaction of GaAs surface with atomic layer deposition of high- k dielectrics was investigated to gain fundamental insights into the chemical properties of GaAs surface oxides and high-k/GaAs interface. Electrical characterization of devices was performed to understand the impact of high-k/GaAs interface on MOS device characteristics in order to form a suitable metal/high-k/GaAs gatestack for future high-speed logic and power devices. Reduction of native oxides on GaAs was found to occur during atomic layer deposition (ALD) of high-k dielectrics- HfO2 and Al2O3/HfO 2 nanolaminates on GaAs. Reaction between ALD metal precursor and native oxides on GaAs was identified to be the cause for consumption of native oxides. It was established that the ALD growth temperature has a strong impact on this phenomenon. During post-dielectric annealing the residual arsenic oxides at the interface decomposed leading to an increase in the interfacial gallium oxides. Presence of gallium oxide, Ga2O3 was identified as a cause for observed frequency dispersion in MOS capacitance-voltage curves indicative of a high interface state density. The chemical properties of the AlGaN/GaN heterostructure surface prepared by wet chemical treatment using HCl/HF and NH4OH solutions were investigated and compared. Both HCl and NH4OH solutions were effective in etching the native oxide layer and reducing the surface carbon content; HCl treatment being slightly more effective. Atomic layer deposition of Al 2O3 on AlGaN/GaN surface revealed a reduction of surface gallium oxides due to the reaction between metal precursor and Ga2O 3. This oxide reduction provides an in-situ ALD surface cleaning action and provides a passivation effect useful for suppressing surface states. The interface and electrical properties of Al2O3 and SiO 2 grown by ALD on HCl-treated AlGaN/GaN surface were investigated. An upward band bending in the semiconductor was observed; Al2O 3 resulting in a greater band bending at the interface than SiO2. SiO2 based device yielded a more positive threshold voltage than Al2O 3 suggesting the potential use of a thin SiO2 interface passivation layer to achieve enhancement mode operation. Energy band alignment of ALD dielectrics- SiO2, HfO2, HfAlO and Al2O 3 on GaN was determined using x-ray photoelectron spectroscopy. Fundamental chemical properties of the AlGaN/GaN heterostructure surfaces, interaction of the AlGaN/GaN surfaces with atomic layer deposition of dielectrics and electrical properties of AlGaN/GaN based MOS devices were studied and are the key to improving the device performance of MOS-HEMT transistors for high-power applications.

Suri, Rahul

391

Electrical characterization of high K dielectrics and metals, modeling of dielectric response, and modification of metal work function  

Microsoft Academic Search

During the deposition of HfO2 gate oxide by atomic layer deposition (ALD) and post deposition annealing, it is observed that SiOx growth on Si, interdiffusion of Hf, Si, and O species, formation of Hf-O-Si bond linkages and amorphous Hf silicates through reactions at internal interfaces, and nucleation and growth of HfO2 occurs. Due to this intermixing, an intermediate layer with

Diefeng Gu

2006-01-01

392

Terahertz Spectroscopy as a non contact estimation technique of defect states in high dielectric constant materials  

NASA Astrophysics Data System (ADS)

A large number of gate dielectric materials have been examined during the past few years to replace Silicon dioxide in the MOSFET industry to reduce gate leakage currents for microfabrication of devices. Among them, Hafnium based materials have become a very promising candidate. In the reported work, the effect of Hafnium dioxide films on p-type silicon substrates has been investigated and compared with conventional dielectric material, Silicon dioxide, using CW visible pump/THz probe spectroscopy. Drude analysis of the experimentally obtained differential transmission spectra evaluates the electric permittivity of the interfacial layer and the calculated defect density is found to be higher for HfO2 than for SiO2 which agrees with Hall measurements. Additional measurements on Silicon Nitride deposition and photoresist coated p+ Silicon on p-type silicon wafers without any oxide gave an interfacial defect density 50 times higher than that of SiO2/p+ interface. Results indicate that the mobility of the layer underneath Hafnium is less than that of Silicon. Hence the present study emphasizes the advantage of THz spectroscopy as a non-contact tool for semiconductor metrological applications.

Sengupta, Amartya; Bandyopadhyay, Aparajita; Altan, Hakan; Federici, John; Grebel, Haim

2006-03-01

393

Quenched transmission of light through ultrathin metal films  

NASA Astrophysics Data System (ADS)

We discuss optical properties of ultrathin metal films, with particular attention to the phenomenon of quenched transmission. Transmission of light through an optically ultrathin metal film with a thickness comparable to its skin depth is significant. We demonstrate the quenched transmission through the ultrathin metal films when they are periodically modulated. We also discuss the physics behind it and explain how this abnormal phenomenon is ascribed to surface plasmon resonance effects.

Xiao, Sanshui; Mortensen, N. Asger

2011-09-01

394

A study on the evolution of dielectric function of ZnO thin films with decreasing film thickness  

NASA Astrophysics Data System (ADS)

Dielectric function, band gap, and exciton binding energies of ultrathin ZnO films as a function of film thickness have been obtained with spectroscopic ellipsometry. As the film thickness decreases, both real (?1) and imaginary (?2) parts of the dielectric function decrease significantly, and ?2 shows a blue shift. The film thickness dependence of the dielectric function is shown related to the changes in the interband absorption, discrete-exciton absorption, and continuum-exciton absorption, which can be attributed to the quantum confinement effect on both the band gap and exciton binding energies.

Li, X. D.; Chen, T. P.; Liu, P.; Liu, Y.; Liu, Z.; Leong, K. C.

2014-03-01

395

Characterization of ALD Beryllium Oxide as a Potential High- k Gate Dielectric for Low-Leakage AlGaN/GaN MOSHEMTs  

NASA Astrophysics Data System (ADS)

The chemical and electrical characteristics of atomic layer deposited (ALD) beryllium oxide (BeO) on GaN were studied via x-ray photoelectron spectroscopy, current-voltage, and capacitance-voltage measurements and compared with those of ALD Al2O3 and HfO2 on GaN. Radiofrequency (RF) and power electronics based on AlGaN/GaN high-electron-mobility transistors are maturing rapidly, but leakage current reduction and interface defect ( D it) minimization remain heavily researched. BeO has received recent attention as a high- k gate dielectric due to its large band gap (10.6 eV) and thermal stability on InGaAs and Si, but little is known about its performance on GaN. Unintentionally doped GaN was cleaned in dilute aqueous HCl immediately prior to BeO deposition (using diethylberyllium and H2O precursors). Formation of an interfacial layer was observed in as-deposited samples, similar to the layer formed during ALD HfO2 deposition on GaN. Postdeposition anneal (PDA) at 700°C and 900°C had little effect on the observed BeO binding state, confirming the strength of the bond, but led to increased Ga oxide formation, indicating the presence of unincorporated oxygen in the dielectric. Despite the interfacial layer, gate leakage current of 1.1 × 10-7 A/cm2 was realized, confirming the potential of ALD BeO for use in low-leakage AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors.

Johnson, Derek W.; Yum, Jung Hwan; Hudnall, Todd W.; Mushinski, Ryan M.; Bielawski, Christopher W.; Roberts, John C.; Wang, Wei-E.; Banerjee, Sanjay K.; Harris, H. Rusty

2014-01-01

396

Homogeneous switching in ultrathin ferroelectric films.  

PubMed

It is well known that there are two possible switching mechanisms in ferroelectric crystals and films (see, e.g., Tagantsev et al 2010 Domains in Ferroic Crystals and Thin Films (Berlin: Springer)). The first mechanism, which follows from the mean-field theory of Landau-Ginzburg, is a homogeneous one and does not connect domains. This mechanism was never observed before 1998. The second mechanism, connected with nucleation and domain movement, is common for the ferroelectrics and is well known from the time of domain discovery (1956). In the present paper the existence of a homogeneous mechanism of switching in ultrathin copolymer films is confirmed by piezoresponse force microscopy. The results of the present paper permit us to suppose that homogeneous switching exists in other ultrathin ferroelectric films. PMID:22155978

Gaynutdinov, R; Yudin, S; Ducharme, S; Fridkin, V

2012-01-11

397

High efficiency ultrathin coplanar back contact cells  

NASA Technical Reports Server (NTRS)

Efforts to fabricate high efficiency, ultrathin coplanar back contact cells are described. Included is a description of design considerations, cell fabrication, and theoretical and experimental analyses of loss mechanisms. The results of these efforts has been the fabrication of a 11.8% AM0 efficient, 50 micron cell when measured at 25 C. Design and process changes required to increase the efficiency are indicated.

Storti, G.; Wrigley, C.; Wohlgemuth, J.; Whitehouse, D.; Scheinine, A.

1980-01-01

398

Improvement of gate dielectric reliability for p\\/sup +\\/ poly MOS devices using remote PECVD top nitride deposition on thin gate oxides  

Microsoft Academic Search

Dual layer dielectrics have been formed by remote PECVD of ultra-thin (0.4\\/spl sim\\/1.2 nm) nitrides on thin thermal oxides grown on n-type Si(100) substrates. Activation of boron-implanted p\\/sup +\\/ polycrystalline silicon gate electrodes was accomplished by a high temperature anneal for 1\\/spl sim\\/4 minutes at 1000\\/spl deg\\/C. Boron penetration through the dielectric film to the n-type substrate was investigated by

Yider Wu; Gerald Lucovsky; H. Z. Massoud

1998-01-01

399

First principles investigation of the dielectric function of gold under ultrafast laser excitation  

Microsoft Academic Search

Recently, a quasi-steady state in ultrathin, ˜30 nm gold foils exposed to an ultrafast laser pulse has been observed, which includes an enhanced interband transition peak at 2.6 eV in the imaginary part of the dielectric function [1]. Simulations of this system assuming a two-temperature model for the electronic and ionic degrees of freedom do not provide this enhancement in

Tadashi Ogitsu; David Prendergast; Eric Schwegler; Yuan Ping; Andrew Ng

2008-01-01

400

Imaging Electrons in Ultra-thin Nanowires  

NASA Astrophysics Data System (ADS)

Ultra-thin semiconductor nanowires are promising systems in which to explore novel low-dimensional physics and are attractive candidates for future nanoelectronics. Ultra-thin nanowires with diameters of 20 to 30 nm are essentially one-dimensional (ID) for moderate electron number, because only one radial subband is occupied. Low-temperature scanning gate microscopy is especially well suited for improving our understanding of nanowires in order to optimize the construction of nanowire systems. We use a home-built liquid-He cooled scanning gate microscope (SGM) to probe and manipulate electrons beneath the surface of devices. The SGM's conductance images are obtained by scanning the charged SGM tip above the sample and recording the change in conductance through the device as a function of tip position. We present simulations of extracting the amplitude of the 1D electron wavefunction along the length of the quantum dot in an ultra-thin InAs/InP heterostructure nanowire (diameter = 30 nm) using a SGM. A weakly perturbing SGM tip slightly dents the electron wavefunction inside the quantum dot, and we propose measuring the change in energy of the dot due to the perturbation as a function of tip position. By measuring the change in energy of the dot and by knowing the form of the tip potential, the amplitude of the wavefunction can be found. This extraction technique could serve as a powerful tool to improve our understanding of electron behavior in quasi-1 D systems. We have used our SGM to image the conductance through an ultra-thin (diameter ˜ 30 nm) 1nAs nanowire with two InP barriers. Our imaging technique provides detailed information regarding the position and flow of electrons in the nanowire. We demonstrate that the charged SPM tip's position or voltage can be used to control the number of electrons on the quantum dots. We spatially locate three quantum dots in series along the length of the ultra-thin nanowire. Using energy level spectroscopy and the conductance images, we find the length of all three of the dots, and we determine the dots' relative coupling strength.

Boyd, Erin E.

401

Onset of bonding plasmon hybridization preceded by gap modes in dielectric splitting of metal disks.  

PubMed

Dielectric splitting of nanoscale disks was studied experimentally and via finite-difference time-domain (FDTD) simulations through systematic introduction of multiple ultrathin dielectric layers. Tunable, hybridized dark bonding modes were seen with first-order gap modes preceding the appearance of bonding dipole-dipole disk modes. The observed bright dipolar mode did not show the energy shift expected from plasmon hybridization but activated dark higher order gap modes. Introducing lateral asymmetry was shown to remodel the field distribution resulting in 3D asymmetry that reoriented the dipole orientation away from the dipole of the elementary disk modes. PMID:24219491

Frederiksen, Maj; Bochenkov, Vladimir E; Ogaki, Ryosuke; Sutherland, Duncan S

2013-12-11

402

Mechanical Properties of Robust Ultrathin Silk Fibroin Films.  

National Technical Information Service (NTIS)

Robust ultrathin multilayer films of silk fibroin were fabricated by spin coating and spin-assisted layer-by-layer assembly and their mechanical properties were studied both in tensile and compression modes for the first time. The ultrathin films were cha...

C. Jiang M. K. Gupta R. Gunawidjaja X. Wang Y. H. Lin

2007-01-01

403

Interfacial study and band alignment of ultrathin La2Hf2O7 films on GaAs substrates  

NASA Astrophysics Data System (ADS)

We report ultrathin amorphous La2Hf2O7 (LHO) films grown on p-GaAs (0 0 1) substrates as high-k gate dielectric using the pulsed laser deposition method. Interfacial characterization of the LHO/GaAs has been carried out. It shows that the interfacial layer with a thickness of less than 0.5 nm is composed of Ga2O3. Experimental results show that the 5.7 ± 0.1 eV bandgap of LHO is aligned to the bandgap of GaAs with a valence band offset of 3.15 ± 0.05 eV and a conduction band offset of 1.1 ± 0.1 eV. Capacitance-voltage and current-voltage measurements indicate that LHO could be a promising gate dielectric for GaAs metal-oxide-semiconductor devices.

Wei, F.; Xiong, Y.-H.; Zhang, X.-Q.; Du, J.; Tu, H.-L.

2013-09-01

404

Ultra-thin body poly(3-hexylthiophene) transistors with improved short-channel performance  

NASA Astrophysics Data System (ADS)

The microstructure and charge transport properties of binary blend of regioregiolar (rr) and regiorandom(RRa) poly(3-hexylthiophene) (P3HT) are investigated. X-ray diffraction study shows vertical phase separation in the blend films, with rr-P3HT crystallized at the semiconductor/dielectric interface. These thin film transistors with layered structure preserve high field effect mobility when rr-P3HTcontents are reduced to as low as 5.6% where the channel thickness is only a few nanometers. As a result of this ultra-thin active layer at interface, short channel effects due to bulk currents are eliminated, suggesting a new route to fabricate high performance, small size and reliable electronic devices.

Wang, Chenchen; Rivnay, Jonathan; Himmelberger, Scott; Vakhshouri, Kiarash; Gomez, Enrique D.; Salleo, Alberto

2012-02-01

405

Ultrathin body poly(3-hexylthiophene) transistors with improved short-channel performance.  

PubMed

The microstructure and charge transport properties of binary blends of regioregular (rr) and regiorandom (RRa) poly(3-hexylthiophene) (P3HT) are investigated. X-ray diffraction of the blended films is consistent with a vertically separated structure, with rr-P3HT preferentially crystallizing at the semiconductor/dielectric interface. Thin film transistors made with these blended films preserve high field effect mobility with rr-P3HTcontent as low as 5.6%. In these dilute blends, we estimate that the thickness of rr-P3HT in the channel is only a few nanometers. Significantly, as a result of such an ultrathin active layer at the interface, short channel effects due to bulk currents are eliminated, suggesting a new route to fabricate high-performance, short-channel, and reliable organic electronic devices. PMID:23429794

Wang, Chenchen; Rivnay, Jonathan; Himmelberger, Scott; Vakhshouri, Kiarash; Toney, Michael F; Gomez, Enrique D; Salleo, Alberto

2013-04-10

406

Glass transition and segmental dynamics of ultrathin poly(bisphenol a carbonate) films  

NASA Astrophysics Data System (ADS)

Broadband dielectric spectroscopy (BDS), capacitive scanning dilatometry (CSD) and differential ac-chip calorimetry (DACC) were used to examine the glass transition and segmental dynamics of ultrathin poly(bisphenol A carbonate) (PBAC) films. An increase of Vogel temperature (T0) as well as glass transition temperature (Tg) with decreasing film thickness was observed when the thickness is less than 20 nm. Moreover, the segmental relaxation time at a fixed temperature was found to increase for the aluminium (Al) capped PBAC films (<20 nm) in the BDS measurements, whereas in the DACC measurements no thickness dependency of the segmental dynamics was detected within the experimental error limit for the supported PBAC films (10-55 nm). These properties are discussed in terms of the thin film geometry and the relevant interfacial interaction between the polymer and the substrate.

Yin, Huajie; Schönhals, Andreas

2012-07-01

407

A physical model for the hysteresis phenomenon of the ultrathin ZrO2 film  

NASA Astrophysics Data System (ADS)

This work studies and presents an inner-interface trapping physical model for the ultra-thin (effective oxide thickness=15 Å) zirconium oxide (ZrO2) film to explain its hysteresis phenomenon. The shift of the capacitance-voltage characteristics swept from accumulation to inversion and then swept back with light illumination is about 110 mV, which is larger than the shift without light illumination (~45 mV). The mobile ion effect is obviated using bias-temperature stress measurement. The proposed model successfully explains not only the phenomenon but also the thickness effect for the capacitance-voltage characteristics and the different turn-around voltages of the current density-voltage characteristics of the zirconium dielectrics.

Wang, J. C.; Chiao, S. H.; Lee, C. L.; Lei, T. F.; Lin, Y. M.; Wang, M. F.; Chen, S. C.; Yu, C. H.; Liang, M. S.

2002-10-01

408

Dielectric properties of thin insulating layers measured by Electrostatic Force Microscopy  

NASA Astrophysics Data System (ADS)

In order to measure the dielectric permittivity of thin insulting layers, we developed a method based on electrostatic force microscopy (EFM) experiments coupled with numerical simulations. This method allows to characterize the dielectric properties of materials without any restrictions of film thickness, tip radius and tip-sample distance. The EFM experiments consist in the detection of the electric force gradient by means of a double pass method. The numerical simulations, based on the equivalent charge method (ECM), model the electric force gradient between an EFM tip and a sample, and thus, determine from the EFM experiments the relative dielectric permittivity by an inverse approach. This method was validated on a thin SiO2 sample and was used to characterize the dielectric permittivity of ultrathin poly(vinyl acetate) and polystyrene films at two temperatures.

Riedel, C.; Arinero, R.; Tordjeman, Ph.; Ramonda, M.; Lévêque, G.; Schwartz, G. A.; de Oteyza, D. G.; Alegría, A.; Colmenero, J.

2010-04-01

409

Facile synthesis of ultrathin lepidocrocite nanosheets from layered precursors.  

PubMed

Ultrathin two-dimensional nanosheets have been widely studied because of their peculiar properties and promising applications. As a typical layered material, successful exfoliation of freestanding ultrathin lepidocrocite (?-FeOOH) nanosheets from the bulk material has not been reported to date. Herein, we report a facile synthetic route to prepare ultrathin lepidocrocite nanosheets with a thickness of approximately 2-3?nm from FeOx -propanediol layered precursors through weakening of the hydrogen bonds during the crystallization process. The ultrathin morphology and single-crystal structure of the nanosheets were confirmed by transmission electron microscopy, X-ray diffraction, and atomic force microscopy. The formation process of these nanosheets demonstrated simultaneous exfoliation and crystallization of lepidocrocite in basic aqueous solution. The obtained ultrathin nanosheets exhibited a much lower Néel temperature (18.3?K) than bulk lepidocrocite and weak ferromagnetic behavior below this temperature. PMID:24706619

Yang, Yijun; Zhong, Yeteng; Wang, Xi; Ma, Ying; Yao, Jiannian

2014-06-01

410

Effects of gate-first and gate-last process on interface quality of In0.53Ga0.47As metal-oxide-semiconductor capacitors using atomic-layer-deposited Al2O3 and HfO2 oxides  

NASA Astrophysics Data System (ADS)

We have investigated the effects of gate-first and gate-last process on oxide/InGaAs interface quality using In0.53Ga0.47As metal-oxide-semiconductor capacitors (MOSCAPs) with atomic-layer-deposited (ALD) oxides. Sequence of source/drain activation anneal in the process results in remarkable electrical and physical difference. Applying gate-last process provides significant frequency dispersion reduction and interface trap density reduction for InGaAs MOSCAPs compared to gate-first process. A large amount of In-O, Ga-O, and As-As bonds was observed on InGaAs surface after gate-first process while no detectable interface reaction after gate-last process. Electrical and physical results also show that ALD Al2O3 exhibits better interface quality on InGaAs than HfO2.

Zhao, Han; Huang, Jeff; Chen, Yen-Ting; Yum, Jung Hwan; Wang, Yanzhen; Zhou, Fei; Xue, Fei; Lee, Jack C.

2009-12-01

411

Dielectric and complex impedance properties of tetravalent hafnium (HF 4+) integrated cobalt ferrite  

NASA Astrophysics Data System (ADS)

The work presented in this thesis was carried out to understand the effects of tetravalent hafnium (Hf4+) ion on the crystal structure and phase, surface morphology, electrical, dielectric and complex impedance properties of cobalt ferrite (CoFe2O4; CFO). Hafnium incorporated cobalt ferrite, CoFe2-xHfxO4, with x = 0.00, 0.05, 0.075, 0.10, 0.15 and 0.20 were prepared by the standard solid state ceramic synthesis method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) characterizations were performed to determine the structural properties. Most important aspect of this study is to explore the dielectric and complex impedance properties as a function of variable temperature (T=300-1000 K) and frequency (f=20 Hz -1 MHz). Room temperature and the temperature dependence of dielectric constant, loss factor, complex impedance, and the ac resistivity measurements enabled us to understand the effect of temperature and frequency on the electrical and dielectric properties on CoFe2-xHfxO4 and, thus, to derive structure-property relation. X-ray diffraction (XRD) patterns for Hf-incorporated CFO confirm the formation of majority of CFO spinel [with space group Fd3m (227)] phase, in addition to the small amount of HfO2 monoclinic [space group, P1 21/c (14)] phase leading to formation of CFO-Hf composites. The lattice constant values derived from XRD for CFO-Hf were found to increase from 8.374 A (x = 0.000) to 8.391 A (x = 0.200). The lattice expansion is significant at the very first step of Hf-incorporation and then slows down with progressive Hf-incorporation. SEM imaging analysis indicates that Hf resides at the grain boundaries for CFO-Hf. The dielectric constant (epsilon') of CFO-Hf is T-independent at T<450 K, at which point increasing trend prevails. A grain bulk-boundary based two-layer model, where semiconducting-grains separated by insulating-grain boundaries, satisfactorily accounts for epsilon- T (>450 K) variation. Correspondingly, electrical responses in impedance formalism are attributed to the grain and grain-boundary effects, respectively, which also accounts for the observed two dielectric-relaxations. The results demonstrate that the dielectric phenomena in CFO-Hf can be tailored by tuning Hf-concentration.

Sanchez, Luis

412

Measurement of effective carrier lifetime at the semiconductor-dielectric interface by Photoconductive Decay (PCD) Method  

NASA Astrophysics Data System (ADS)

The semiconductor-dielectric interface is of key importance to the performance of Metal-Oxide-Semiconductor transistors (MOSFETs). The near-surface Photoconductance Decay (ns-PCD) method using probe contacts is shown in this study to be very useful in measuring effective carrier lifetime at the semiconductor-dielectric interface. By doing so, it provides direct information on the condition of the charge transport environment in the MOSFET channel without a need to fabricate a transistor. The way measurement is implemented depends on the thickness of dielectric. For dielectric layers thicker than about 5 nm, etched windows in the dielectric layer are necessary to achieve an ohmic contact with the semiconductor layer. For dielectric layers thinner than about 5 nm, however, the ohmic contact to the semiconductor substrate, essential to the performance of this measurement, is established using probes and electrical contact formation process. The measurements were performed on thermally oxidized Si-SiO2 structures as well as Si-Al2O3 (3 nm) and Si-Ta2O5 (3 nm) structures formed by means of Atomic Layer Deposition (ALD). The results obtained demonstrate that the PCD method adapted as discussed in this work can be very useful in monitoring condition of semiconductor - ultra-thin (<5 nm) dielectric interface by measuring carrier lifetime in the as-processed samples, i.e. without subjecting it to any processing step beyond dielectric deposition.

Drummond, P. J.; Bhatia, D.; Ruzyllo, J.

2013-03-01

413

Dielectric characterisation of soil  

Microsoft Academic Search

The potential of dielectric measuring techniques for soil characterisation has not been fully explored. This is attributed to the complex and incomplete theory on dielectrics, as well as to the lack of sensors suited for practical applications.The theory on dielectric properties of soils is described, evaluated, and expanded. Colloidal polarisation of soil particles appears to be negligible. The polarisability of

M. A. Hilhorst

1998-01-01

414

Characterization of growth and thermal behaviors of thin films for the advanced gate stack grown by chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Studies have been done on the materials for alternative gate dielectrics (high-k) and a metal gate electrode, which will replace conventional SiO 2 gate dielectric and poly silicon gate electrode, for the sub-100 nm CMOS technologies. Ultrathin HfO2 films prepared by chemical vapor deposition on Si(100) were annealed in high vacuum or N2 ambient at high temperature and their thermal stability was measured. Based on in-situ XPS, annealing HfO2 films grown by CVD on clean Si(100) leads to silicide formation at 950°C for ultrahigh vacuum but not 4 Torr of N 2. For an HfO2 film capped with amorphous Si, silicide does form upon annealing in 4 torr, but not 760 torr, of N2. TEM shows when hafnium silicide forms, it forms discontinuous islands. HfON thin film prepared by chemical vapor deposition on silicon substrate showed superior thermal stability compared to HfO2 thin film. X-ray photoelectron spectroscopy studies shows that HfON thin film is chemically stable in contact with silicon up to 1000°C under high vacuum. Excellent resistance to crystallization of HfON thin film during high temperature process is proven by a glancing angle XRD. MOS devices using HfON dielectric thin film showed better electrical properties than HfO2. CVD TaN film exhibited excellent thermal stability in terms of chemical, structural, and electrical aspects. PMOS compatible work function (˜5.0 eV) and the excellent electrical performance of CVD TaN gate electrode suggest that it is a promising candidate to replace p+ poly silicon for sub-100 nm CMOS technology.

Jeon, Taek Soo

415

An ultrathin but nearly perfect direct current electric cloak  

NASA Astrophysics Data System (ADS)

We propose and experimentally demonstrate an ultrathin but nearly perfect dc electric invisibility cloak. In the dc limit, transformation optics reduces to transformation electrostatics. Based on a special coordinate transformation, we derive a nearly perfect dc electric cloak which is composed of homogeneous and anisotropic conducting material. Due to the homogeneity feature, the dc cloak is realized using an ultrathin dc metamaterial with only one-unit-cell thickness, which is the ultra limit for practical artificial materials. Although ultrathin, our experimental results show that the dc cloak has excellent performance with nearly perfect cloaking behaviour.

Xiang Jiang, Wei; Yang Luo, Chen; Lei Mei, Zhong; Jun Cui, Tie

2013-01-01

416

Static properties of equilibrium polymers confined in ultrathin films  

NASA Astrophysics Data System (ADS)

The static properties of equilibrium polymer melts confined in ultrathin films are studied by means of Monte Carlo simulations of a lattice model: the bond fluctuation model. In this work we focus on the effects of ultrathin film confinement between two parallel and neutral walls on chain size and molecular weight distribution. We compare our numerical results to analytical calculations by Semenov and Johner [Eur. Phy. J. E, 12, 469 (2003)] who predicted for ultrathin films, logarithmic corrections to the leading mean-field behavior. Our simulation data are compatible with the theoretical results.

Cavallo, Anna; Wittmer, Joachim P.; Johner, Albert; Baschnagel, Joerg

2008-03-01

417

Ultrathin optical panel and a method of making an ultrathin optical panel  

SciTech Connect

An ultrathin optical panel, and a method of producing an ultrathin optical panel, are disclosed, including stacking a plurality of glass sheets, which sheets may be coated with a transparent cladding substance or may be uncoated, fastening together the plurality of stacked coated glass sheets using an epoxy or ultraviolet adhesive, applying uniform pressure to the stack, curing the stack, sawing the stack to form an inlet face on a side of the stack and an outlet face on an opposed side of the stack, bonding a coupler to the inlet face of the stack, and fastening the stack, having the coupler bonded thereto, within a rectangular housing having an open front which is aligned with the outlet face, the rectangular housing having therein a light generator which is optically aligned with the coupler. The light generator is preferably placed parallel to and proximate with the inlet face, thereby allowing for a reduction in the depth of the housing.

Biscardi, Cyrus (Bellport, NY); Brewster, Calvin (North Patchogue, NY); DeSanto, Leonard (Patchogue, NY); Veligdan, James T. (Manorville, NY)

2001-10-09

418

Ultrathin Optical Panel And A Method Of Making An Ultrathin Optical Panel.  

DOEpatents

An ultrathin optical panel, and a method of producing an ultrathin optical panel, are disclosed, including stacking a plurality of glass sheets, which sheets may be coated with a transparent cladding substance or may be uncoated, fastening together the plurality of stacked coated glass sheets using an epoxy or ultraviolet adhesive, applying uniform pressure to the stack, curing the stack, sawing the stack to form an inlet face on a side of the stack and an outlet face on an opposed side of the stack, bonding a coupler to the inlet face of the stack, and fastening the stack, having the coupler bonded thereto, within a rectangular housing having an open front which is aligned with the outlet face, the rectangular housing having therein a light generator which is optically aligned with the coupler. The light generator is preferably placed parallel to and proximate with the inlet face, thereby allowing for a reduction in the depth of the housing.

Biscardi, Cyrus (Bellport, NY); Brewster, Calvin (North Patchogue, NY); DeSanto, Leonard (Patchogue, NY); Veligdan, James T. (Manorville, NY)

2005-05-17

419

Ultrathin optical panel and a method of making an ultrathin optical panel  

DOEpatents

An ultrathin optical panel, and a method of producing an ultrathin optical panel, are disclosed, including stacking a plurality of glass sheets, which sheets may be coated with a transparent cladding substance or may be uncoated, fastening together the plurality of stacked coated glass sheets using an epoxy or ultraviolet adhesive, applying uniform pressure to the stack, curing the stack, sawing the stack to form an inlet face on a side of the stack and an outlet face on an opposed side of the stack, bonding a coupler to the inlet face of the stack, and fastening the stack, having the coupler bonded thereto, within a rectangular housing having an open front which is aligned with the outlet face, the rectangular housing having therein a light generator which is optically aligned with the coupler. The light generator is preferably placed parallel to and proximate with the inlet face, thereby allowing for a reduction in the depth of the housing.

Biscardi, Cyrus (Bellport, NY); Brewster, Calvin (North Patchogue, NY); DeSanto, Leonard (Patchogue, NY); Veligdan, James T. (Manorville, NY)

2003-02-11

420

Ultrathin optical panel and a method of making an ultrathin optical panel  

DOEpatents

An ultrathin optical panel, and a method of producing an ultrathin optical panel, are disclosed, including stacking a plurality of glass sheets, which sheets may be coated With a transparent cladding substance or may be uncoated, fastening together the plurality of stacked coated glass sheets using an epoxy or ultraviolet adhesive, applying uniform pressure to the stack, curing the stack, sawing the stack to form an inlet face on a side of the stack and an outlet face on an opposed side of the stack, bonding a coupler to the inlet face of the stack, and fastening the stack, having the coupler bonded thereto, within a rectangular housing having an open front which is aligned with the outlet face, the rectangular housing having therein a light generator which is optically aligned with the coupler. The light generator is preferably placed parallel to and proximate with the inlet face, thereby allowing for a reduction in the depth of the housing.

Biscardi, Cyrus (Bellport, NY); Brewster, Calvin (North Patchogue, NY); DeSanto, Leonard (Patchogue, NY); Veligdan, James T. (Manorville, NY)

2002-01-01

421

Ultrathin Optical Panel And A Method Of Making An Ultrathin Optical Panel.  

DOEpatents

An ultrathin optical panel, and a method of producing an ultrathin optical panel, are disclosed, including stacking a plurality of glass sheets, which sheets may be coated with a transparent cladding substance or may be uncoated, fastening together the plurality of stacked coated glass sheets using an epoxy or ultraviolet adhesive, applying uniform pressure to the stack, curing the stack, sawing the stack to form an inlet face on a side of the stack and an outlet face on an opposed side of the stack, bonding a coupler to the inlet face of the stack, and fastening the stack, having the coupler bonded thereto, within a rectangular housing having an open front which is aligned with the outlet face, the rectangular housing having therein a light generator which is optically aligned with the coupler. The light generator is preferably placed parallel to and proximate with the inlet face, thereby allowing for a reduction in the depth of the housing.

Biscardi, Cyrus (Bellport, NY); Brewster, Calvin (North Patchoque, NY); DeSanto, Leonard (Patchoque, NY); Veligdan, James T. (Manorville, NY)

2005-02-15

422

Characterization and Metrology of Medium Dielectric Constant Gate Dielectric Films  

Microsoft Academic Search

The characterization and optical metrology of physical properties of thin dielectric films and film stacks composed of metal oxides with static dielectric constants from ? ? 4t o? ? 25 is reviewed. These dielectric films are designed to mimic the behavior of silicon dioxide gate dielectrics of 1 to 2 nm thickness, with the elevated dielectric constant allowing a gate

A. C. Diebold; W. W. Chism

423

Study on Surface Energy of Ultra-thin Film  

NASA Astrophysics Data System (ADS)

The dependences of surface energy on ultra-thin film thickness are investigated experimentally and theoretically. Langmuir-Blodgett (LB) film and perfluoropolyether (PFPE) lubricant on solid substrates are used as ultra-thin film samples. Surface energies as a function of film thickness are experimentally obtained from contact angle measurements. The theoretical equation of the dispersive component of the surface energy of ultra-thin film is derived from the corrected van der Waals pressure equation for a multilayered system proposed by the authors. The theoretical values are found to agree with the experimental values. The theoretical equation presented in this study is considered to be useful in predicting the surface energy of an ultra-thin film on a solid substrate.

Matsuoka, Hiroshige; Ono, Katsunori; Fukui, Shigehisa

424

Nanopyramid structure for ultrathin c-Si tandem solar cells.  

PubMed

Recently, ultrathin crystalline silicon solar cells have gained tremendous interest because they are deemed to dramatically reduce material usage. However, the resulting conversion efficiency is still limited by the incomplete light absorption in such ultrathin devices. In this letter, we propose ultrathin a-Si/c-Si tandem solar cells with an efficient light trapping design, where a nanopyramid structure is introduced between the top and bottom cells. The superior light harvesting results in a 48% and 35% remarkable improvement of the short-circuit current density for the top and bottom cells, respectively. Meanwhile, the use of SiOx mixed-phase nanomaterial helps to provide the maximum light trapping without paying the price of reduced electrical performance, and conversion efficiencies of up to 13.3% have been achieved for the ultrathin tandem cell employing only 8 ?m of silicon, which is 29% higher than the result obtained for the planar cell. PMID:24730470

Li, Guijun; Li, He; Ho, Jacob Y L; Wong, Man; Kwok, Hoi Sing

2014-05-14

425

The Thickness Dependence of Optical Constants of Ultrathin Iron Films  

NASA Astrophysics Data System (ADS)

Ultrathin iron films with different thicknesses from 7.1 to 51.7 nm are deposited by magnetron sputtering and covered by tantalum layers protecting them from being oxidized. These ultrathin iron films are studied by spectroscopic ellipsometry and transmittance measurement. An extra tantalum film is deposited under the same sputtering conditions and its optical constants and film thickness are obtained by a combination of ellipsometry and transmission measurement. After introducing these obtained optical constants and film thickness into the tantalum-iron film, the optical constants and film thicknesses of ultrathin iron films with different thicknesses are obtained. The results show that combining ellipsometry and transmission measurement improves the uniqueness of the obtained film thickness. The optical constants of ultrathin iron films depend strongly on film thicknesses. There is a broad absorption peak at about 370 nm and it shifts to 410 nm with film thickness decreasing.

Gao, Shang; Lian, Jie; Sun, Xiao-Fen; Wang, Xiao; Li, Ping; Li, Qing-Hao

2013-02-01

426

Ion-beam-deposited ultrathin transparent metal contacts  

Microsoft Academic Search

Using ion-beam sputtering we have prepared ultrathin transparent metal contacts with large broad-band optical transmittance and low electrical sheet resistance. Metal films deposited by ion-beam sputtering have exceptionally small surface roughness, and films as thin as about 20 Å are continuous and conductive, and provide optical transmittance as large as 80%. Ultrathin transparent metal contacts provide a number of advantages

Hagen Klauk; Jiunn-Ru Huang; Jonathan A Nichols; Thomas N Jackson

2000-01-01

427

Nanocavity enhancement for ultra-thin film optical absorber.  

PubMed

A fundamental strategy is developed to enhance the light-matter interaction of ultra-thin films based on a strong interference effect in planar nanocavities, and overcome the limitation between the optical absorption and film thickness of energy harvesting/conversion materials. This principle is quite general and is applied to explore the spectrally tunable absorption enhancement of various ultra-thin absorptive materials including 2D atomic monolayers. PMID:24616090

Song, Haomin; Guo, Luqing; Liu, Zhejun; Liu, Kai; Zeng, Xie; Ji, Dengxin; Zhang, Nan; Hu, Haifeng; Jiang, Suhua; Gan, Qiaoqiang

2014-05-01

428

Ultra-thin microporous/hybrid materials  

DOEpatents

Ultra-thin hybrid and/or microporous materials and methods for their fabrication are provided. In one embodiment, the exemplary hybrid membranes can be formed including successive surface activation and reaction steps on a porous support that is patterned or non-patterned. The surface activation can be performed using remote plasma exposure to locally activate the exterior surfaces of porous support. Organic/inorganic hybrid precursors such as organometallic silane precursors can be condensed on the locally activated exterior surfaces, whereby ALD reactions can then take place between the condensed hybrid precursors and a reactant. Various embodiments can also include an intermittent replacement of ALD precursors during the membrane formation so as to enhance the hybrid molecular network of the membranes.

Jiang, Ying-Bing (Albuquerque, NM); Cecchi, Joseph L. (Albuquerque, NM); Brinker, C. Jeffrey (Albuquerque, NM)

2012-05-29

429

Ultrathin Reflective Flexible Liquid Crystal Display Film  

NASA Astrophysics Data System (ADS)

In this investigation, we present a thin reflective liquid crystal film with a mixed-mode twisted nematic mode. A low-temperature alignment process is used to obtain good orientation of the liquid crystal molecules. A microcell process is utilized to maintain a uniform cell gap of the flexible display under various bending conditions. To simplify the structure of a flexible mixed-mode twisted nematic liquid crystal display film, a layer of Zeonor optical plastic material is used in place of conventional plastic substrates; this material exhibits quarter wave retardation. The ultrathin device exhibits good cell gap uniformity, a high reflectivity of 35%, and a short response time of 6.67 ms.

Liu, Kang-Hung; Shieh, Han-Ping D.

2012-04-01

430

Self-Organized Ultrathin Oxide Nanocrystals  

SciTech Connect

Sub-2-nm (down to one-unit cell) uniform oxide nanocrystals and highly ordered superstructures were obtained in one step using oleylamine and oleic acid as capping and structure directing agents. The cooperative nature of the nanocrystal growth and assembly resulted in mesoscopic one-dimensional ribbon-like superstructures made of these ultrathin nanocrystals. The process reported here is general and can be readily extended to the production of many other transition metal (TiO2, ZnO, Nb2O5) and rare earth oxide (Eu2O3, Sm2O3, Er2O3, Y2O3, Tb2O3, and Yb2O3) systems.

Huo, Ziyang; Tsung, Chia-kuang; Huang, Wenyu; Fardy, Melissa; Yan, Ruoxue; Li, Yadong; Yang, Piedong; Zhang, Xiaofeng

2009-01-08

431

Kinetics of ferroelectric switching in ultrathin films  

NASA Astrophysics Data System (ADS)

The kinetics of polarization switching in ultrathin ferroelectric polymer films exhibit a critical behavior; there is a pronounced slowing just above the coercive field and just below the critical temperature. The critical slowing is observed in the switching kinetics of ferroelectric Langmuir-Blodgett films of 70% vinylidene-fluoride and 30% trifluoroethylene copolymer with thickness up to 30 ML. Thicker films exhibit an exponential dependence on the field and temperature that is normally associated with extrinsic switching by domain nucleation and growth. We show that the critical behavior arises naturally from the dynamics of homogeneous intrinsic switching in the context of mean-field theory. These results have important implications for the modeling and control of the ferroelectric films in nonvolatile computer memories and solid-state data storage media.

Vizdrik, G.; Ducharme, S.; Fridkin, V. M.; Yudin, S. G.

2003-09-01

432

Light trapping in ultrathin plasmonic solar cells.  

PubMed

We report on the design, fabrication, and measurement of ultrathin film a-Si:H solar cells with nanostructured plasmonic back contacts, which demonstrate enhanced short circuit current densities compared to cells having flat or randomly textured back contacts. The primary photocurrent enhancement occurs in the spectral range from 550 nm to 800 nm. We use angle-resolved photocurrent spectroscopy to confirm that the enhanced absorption is due to coupling to guided modes supported by the cell. Full-field electromagnetic simulation of the absorption in the active a-Si:H layer agrees well with the experimental results. Furthermore, the nanopatterns were fabricated via an inexpensive, scalable, and precise nanopatterning method. These results should guide design of optimized, non-random nanostructured back reflectors for thin film solar cells. PMID:20588593

Ferry, Vivian E; Verschuuren, Marc A; Li, Hongbo B T; Verhagen, Ewold; Walters, Robert J; Schropp, Ruud E I; Atwater, Harry A; Polman, Albert

2010-06-21

433

Dielectrophoresis of lossy dielectrics  

SciTech Connect

Dielectrophoresis of a solid particle in a liquid medium is usually studied under the assumption that the dielectrics are ideal. Real dielectrics, however, exhibit nonzero conductivities, and the results are sometimes unpredictable. The particular case of a lossy dielectric sphere in a lossy dielectric liquid is considered. The dielectrophoretic motion following the application of a dc field is studied, and it is shown that the motion is strongly affected by conductivities. From the results it can be deduced, for instance, that the separation of solid particles in liquid media can be based on differences of conductivities rather than differences of permittivities of the two media.

Mognaschi, E.R.; Savini, A.

1985-07-01

434

Integrity of hafnium silicate\\/silicon dioxide ultrathin films on Si  

Microsoft Academic Search

Rapid thermal annealing at 1000 °C of (HfO2)1-x(SiO2)x pseudobinary alloy films deposited on Si were performed in N2 or O2 atmospheres. The effects on the atomic transport, structure, and composition were investigated using isotopic substitution of oxygen, high-resolution transmission electron microscopy, nuclear reaction analyses, narrow nuclear reaction resonance profiling, and grazing angle x-ray reflection.

J. Morais; L. Miotti; G. V. Soares; S. R. Teixeira; R. Pezzi; K. P. Bastos; I. J. R. Baumvol; A. L. P. Rotondaro; J. J. Chambers; M. R. Visokay; L. Colombo

2002-01-01

435

Gaseous dielectrics III  

SciTech Connect

Topics covered at the conference include: basic physics of gaseous dielectrics; basic mechanisms of pre-breakdown; basic mechanisms of breakdown; new gaseous dielectrics; impulse breakdown; time lags and V-t characteristics; surface flashover; decomposition, aging, and bioenvironmental effects; standards and testing; and gas-insulated equipment. Abstracts of individual items from the conference were prepared separately. (GHT)

Christophorou, L.G. (ed.)

1982-01-01

436

Dielectric properties of aerogels  

SciTech Connect

We have measured the real (dielectric constant) and imaginary (loss factor) components of the complex relative permittivity at 298 [degree]K using microwave frequencies (2, 10, and 18--40 GHz), for bulk SiO[sub 2]-aerogels and for two types of organic aerogels, resorcinol-formaldehyde (RF) and melamine-formaldehyde (MF). Measured dielectric constants are found to vary linearly between values of 1.0 and 2.0 for aerogel densities from 10 to 500 kg/m[sup 3]. For the same range of densities, the measured loss tangents vary linearly between values of 2[times]10[sup [minus]4] and 7[times]10[sup [minus]2]. The observed linearity of the dielectric properties with density in aerogels at microwave frequencies shows that their dielectric behavior is more gas-like than solid-like. The dielectric properties of aerogels are shown to be significantly affected by the adsorbed water internal to the bulk material. For example, water accounts for 7% of the dielectric constant and 70% of the loss at microwave frequencies for silica aerogels. Because of their very high porosity, even with the water content, the aerogels are among the few materials exhibiting such low dielectric properties. Our measurements show that aerogels with greater than 99% porosity have dielectric constants less than 1.03; these are the lowest values ever reported for a bulk solid material.

Hrubesh, L.W.; Keene, L.E.; Latorre, V.R. (Chemistry and Material Sciences Department, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States))

1993-07-01

437

Growth of ultrathin SiO2 on Si by surface irradiation with an O2+Ar electron cyclotron resonance microwave plasma at low temperatures  

NASA Astrophysics Data System (ADS)

Ultrathin SiO2 films were grown by Si surface irradiation with an O2+Ar electron cyclotron resonance (ECR) microwave plasma at low temperatures. These films without hydrogen and silicon deposition were easily grown in a few minutes at low temperatures and at relatively low working pressures (1.0-3.9×10-1 Pa). The promoting growth process of an ultrathin oxidized layer (1-9 nm) was analyzed by in situ Fourier transform infrared reflective absorption spectroscopy. By using the sputter erosion technique, the dependence of x-ray photoelectron spectroscopy on the depth profiling of the films was obtained. The compositional deviations of the films from the stoichiometric SiO2 were also discussed in the interface region of Si/SiO2. This study indicated that an O2 ECR microwave plasma was efficient to form controlled ultrathin SiO2 dielectric films. The dependence of the film quality on the working pressure and gas flow rate ratios of the O2 to Ar was discussed.

Liu, Y. C.; Ho, L. T.; Bai, Y. B.; Li, T. J.; Furakawa, K.; Gao, D. W.; Nakashima, H.; Muroaka, K.

1999-02-01

438

Ultrathin PDMS films: Microstructure and metastability  

NASA Astrophysics Data System (ADS)

This dissertation focuses on ultra-thin liquid films, less than a few nanometers thick, of one polymer, polydimethylsiloxane (PDMS). PDMS, a model flexible linear polymer, also plays a very important role in many applications. There have been many speculations about the molecular conformation in these films; the very flexibility of the chains gives many possibilities. This dissertation will present experimental studies exploring both the ordering of the polymer by the substrate, and one of the consequences of such ordering, on water and solid interfaces. Brewster angle microscopy, surface pressure and surface potential measurements were used to test the reasons for the stability of two-dimensional foams in Langmuir monolayers, which are confined at the air/water interface. Such foams are almost universally observed at gas/liquid coexistence. Our advantage in exploring the mechanism for foam stability was the only known exception: PDMS on a surfactant substrate, in contrast with a pure water substrate. The only difference was the average dipole moment density contrast between liquid and gaseous domains, almost absent in the surfactant case. Such contrast leads to long-range repulsion across the foam. This contrast is universal in gas/liquid coexistence. The difference in dipole moment density contrast for the polymer on the two substrates may result from polymer chain conformation, but no direct technique to verify this on liquid surfaces is available. Deuterium nuclear magnetic resonance was applied for the first time to such ultra-thin polymer films on solid substrates, to probe for order in such films. Using an Anopore membrane provided 2 m2 surface area for PDMS film deposition, enough to obtain a DNMR signal from a PDMS monolayer. Polymer side group ordering, induced by the surface, was demonstrated directly, DNMR shows different macromolecular-level dynamics depending on the polymer amount, DNMR data gives insight into the molecular picture of the polymer chain conformations and dynamics. The most probable chain conformation for one monolayer is a flattened, caterpillar-like structure. For thicker films, a flat conformation is also most likely. These conclusions appear to hold on both the native hydrophilic substrate and the hydrophobic substrate where molecular interactions are different.

Primak, Svetlana V.

439

Structural Characterization of Metal-Oxide Based Dielectrics for CMOS Technology  

NASA Astrophysics Data System (ADS)

A variety of metal oxides and silicates have been proposed as alternative gate dielectrics for CMOS technology. A daunting list of materials requirements must be met before any of these materials can substitute for silicon dioxide. We have used a variety of techniques, including medium energy ion scattering (MEIS) and high resolution transmission electron microscopy to investigate the compatibility and robustness of high capacitance ultra-thin films on silicon substrates. Nucleation may also pose significant challenges, as illustrated by growth of ZrO2, which grows well on oxidized surfaces, but poorly on HF etched Si(001). More ideal behavior is observed for Al2O3, which may be considered a model system, since it exhibits many of the properties investigators seek, but suffers from having a modest dielectric constant. We will also examine the strengths and weaknesses of La based dielectrics, which offer a higher dielectric constant, but are highly reactive with Si. This talk will highlight how MEIS analysis, when combined with in situ deposition and processing, is a powerful technique for studying how proposed next-generation dielectrics fare under CMOS processing conditions. Although the task of creating a viable alternative gate dielectric is formidable, it is a prime opportunity for the materials research community to affect future technology.

Copel, Matt

2001-03-01

440

Properties of Hafnium Dioxide Thin-Film Capacitors  

Microsoft Academic Search

Dielectric films of anodically formed HfO2based on Hf films of different degrees of orientation as well as reactively sputtered HfO2films were studied. The anodic oxide grown on oriented Hf films and the reactively sputtered HfO2films were monoclinic and showed partial orientation with the

F. Huber

1971-01-01

441

Enhanced bias stress stability of a-InGaZnO thin film transistors by inserting an ultra-thin interfacial InGaZnO:N layer  

NASA Astrophysics Data System (ADS)

Amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) having an ultra-thin nitrogenated a-IGZO (a-IGZO:N) layer sandwiched at the channel/gate dielectric interface are fabricated. It is found that the device shows enhanced bias stress stability with significantly reduced threshold voltage drift under positive gate bias stress. Based on x-ray photoelectron spectroscopy measurement, the concentration of oxygen vacancies within the a-IGZO:N layer is suppressed due to the formation of N-Ga bonds. Meanwhile, low frequency noise analysis indicates that the average trap density near the channel/dielectric interface continuously drops as the nitrogen content within the a-IGZO:N layer increases. The improved interface quality upon nitrogen doping agrees with the enhanced bias stress stability of the a-IGZO TFTs.

Huang, Xiaoming; Wu, Chenfei; Lu, Hai; Ren, Fangfang; Chen, Dunjun; Zhang, Rong; Zheng, Youdou

2013-05-01

442

Valence Electron Energy-loss Spectroscopy of Ultrathin SrTiO3 Films Grown on Silicon (100) Single Crystal  

SciTech Connect

Valence electron energy-loss spectroscopy is used to investigate the plasmon excitations of ultrathin SrTiO{sub 3} sandwiched between amorphous Si and crystalline Si. Two plasmon excitations were observed, one at 15.8 eV and the other at 28.7 eV. Our calculations, based on dielectric-function theory, suggest that the former peak originates from the coupling of the Si layers and is related to the geometry of the structure, and the latter peak results from the SrTiO{sub 3} bulk plasmon after a redshift. Our findings demonstrate the value of valence electron energy-loss spectroscopy in detecting a local change in the effective electron mass.

Su, D.; Yang, B.; Jiang, N.; Sawicki, M.; Broadbridge, C.; Couillard,, M.; Reiner, J.W.; Walker, F.J.; Ahn, C.H.; Zhu, Y.

2010-03-25

443

Structural and electronic properties of anisotropic ultrathin organic films from dichroic resonant soft x-ray reflectivity  

NASA Astrophysics Data System (ADS)

We developed a quantitative approach for the determination of molecular arrangement and electronic structure in anisotropic organic ultrathin films based on the measurement of polarized reflectivity at the carbon K-edge. The reflectivity spectra were fitted to a parameterized model calculation. The method was applied to a self-assembled monolayer of 1,4-benzenedimethanethiol on gold. To simulate reflectivity, the organic anisotropic film was described by a dielectric tensor, obtained by ab initio calculations for the single molecule and suitable rotations to describe the molecular organization in film domains. Film structure was obtained though the best fit of the simulation to the experiment. Results were consistent with a monolayer-thick film composed of domains of molecules with in-plane isotropic distribution of orientations. In each domain, molecules adopted a standing configuration, with a tilt of 28° relative to the substrate normal. Information on the modification of the molecular electronic states due to chemical bonding was derived.

Pasquali, Luca; Mukherjee, Subhrangsu; Terzi, Fabio; Giglia, Angelo; Mahne, Nicola; Koshmak, Konstantin; Esaulov, Vladimir; Toccafondi, Chiara; Canepa, Maurizio; Nannarone, Stefano

2014-01-01

444

Crystal structure of ultrathin lamellar precipitates  

NASA Astrophysics Data System (ADS)

The crystal structure of lamellar precipitates formed in alloys 1213 (Al-Cu-Ag), V-1461 (Al-Cu-Li) and V-1469 (Al-Cu-Li-Ag) has been studied during age hardening. The experimental studies have been performed using transmission electron microscopy. The precipitates have {111} habits and thicknesses of several atomic planes. In diffraction patterns, these plates give a system of diffuse streaks. These ultrathin plates scatter electrons similar to two-dimensional crystal lattices. It is shown that thin plates of precipitates in alloys 1213, V-1461, and V-1469 give identical systems of diffuse streaks. The two-dimensional crystal lattices that give the system of these streaks have a hexagonal symmetry with the following orientation relationship: {ie481-1} and the lattice parameter a f = 0.495 nm (there is no lattice parameter c f for two-dimensional lattices). A sequence of the steps of reconstruction of the spatial structure of plane precipitates is proposed in terms of their thickness, structures of two-dimensional lattices, and type of precipitates (extrinsic or intrinsic). The influence of Ag on the structure of lamellar precipitates in the V-1469 alloy is discussed.

Alekseev, A. A.; Lukina, E. A.; Klochkova, Yu. Yu.

2013-06-01

445

Versatile ultrathin nanoporous silicon nitride membranes  

PubMed Central

Single- and multiple-nanopore membranes are both highly interesting for biosensing and separation processes, as well as their ability to mimic biological membranes. The density of pores, their shape, and their surface chemistry are the key factors that determine membrane transport and separation capabilities. Here, we report silicon nitride (SiN) membranes with fully controlled porosity, pore geometry, and pore surface chemistry. An ultrathin freestanding SiN platform is described with conical or double-conical nanopores of diameters as small as several nanometers, prepared by the track-etching technique. This technique allows the membrane porosity to be tuned from one to billions of pores per square centimeter. We demonstrate the separation capabilities of these membranes by discrimination of dye and protein molecules based on their charge and size. This separation process is based on an electrostatic mechanism and operates in physiological electrolyte conditions. As we have also shown, the separation capabilities can be tuned by chemically modifying the pore walls. Compared with typical membranes with cylindrical pores, the conical and double-conical pores reported here allow for higher fluxes, a critical advantage in separation applications. In addition, the conical pore shape results in a shorter effective length, which gives advantages for single biomolecule detection applications such as nanopore-based DNA analysis.

Vlassiouk, Ivan; Apel, Pavel Y.; Dmitriev, Sergey N.; Healy, Ken; Siwy, Zuzanna S.

2009-01-01

446

Ultrathin film imaging at 157 nm  

NASA Astrophysics Data System (ADS)

In future lithography the 157 nm wavelength is expected to succeed the 193 nm wavelength in 2004. So an early CARL resist for sub 100 nm resolution was developed at Infineon Technologies within the German BMBF project Laserbasierte Ultraprazisionstechnik - 157 nm Lithographie. Common 248 and 193 nm resist materials have a high absorbance (7- 12micrometers - A main challenge at this short exposure wavelength is the development of a transparent base polymer or the imaging has to be done alternatively with ultra thin films. In contrast to a high transparency of the polymer a high quantum yield for the photo chemicals is required. CARL is a bilayer resist system developed by Siemens/Infineon Technologies. A modified CARL version is presented here for exposures at 157 nm, consisting of a silicon free top resist (Si free CARL as thin imaging layer. A separate silylation step of the structured top resist after exposure and wet development provides a high etch resistance in the dry development step and allows imaging of ultra-thin films with a film thickness of ca. 50 nm. An oxygen plasma is taken to transfer these top resist structures into the up to 300 nm thick underlying Novolac type bottom resist. In dry development. The bottom resist itself provides high etch resistance also for aggressive substrate etch processes.

Rottstegge, Joerg; Herbst, Waltraud; Hien, Stefan; Fuetterer, Gerald; Eschbaumer, Christian; Hohle, Christoph; Schwider, Johannes; Sebald, Michael

2002-07-01

447

Versatile ultrathin nanoporous silicon nitride membranes.  

PubMed

Single- and multiple-nanopore membranes are both highly interesting for biosensing and separation processes, as well as their ability to mimic biological membranes. The density of pores, their shape, and their surface chemistry are the key factors that determine membrane transport and separation capabilities. Here, we report silicon nitride (SiN) membranes with fully controlled porosity, pore geometry, and pore surface chemistry. An ultrathin freestanding SiN platform is described with conical or double-conical nanopores of diameters as small as several nanometers, prepared by the track-etching technique. This technique allows the membrane porosity to be tuned from one to billions of pores per square centimeter. We demonstrate the separation capabilities of these membranes by discrimination of dye and protein molecules based on their charge and size. This separation process is based on an electrostatic mechanism and operates in physiological electrolyte conditions. As we have also shown, the separation capabilities can be tuned by chemically modifying the pore walls. Compared with typical membranes with cylindrical pores, the conical and double-conical pores reported here allow for higher fluxes, a critical advantage in separation applications. In addition, the conical pore shape results in a shorter effective length, which gives advantages for single biomolecule detection applications such as nanopore-based DNA analysis. PMID:19948951

Vlassiouk, Ivan; Apel, Pavel Y; Dmitriev, Sergey N; Healy, Ken; Siwy, Zuzanna S

2009-12-15

448

Improved Dielectric Films For Capacitors  

NASA Technical Reports Server (NTRS)

Dielectric films made from blends of some commercially available high-dielectric-constant cyanoresins with each other and with cellulose triacetate (CTA) have both high dielectric constants and high breakdown strengths. Dielectric constants as high as 16.2. Films used to produce high-energy-density capacitors.

Yen, Shiao-Ping S.; Lewis, Carol R.; Cygan, Peter J.; Jow, T. Richard

1994-01-01

449

Agricultural applications of dielectric measurements  

Microsoft Academic Search

A brief historical perspective on dielectric properties of agricultural products is presented, including their use for rapid measurement of moisture content in grain and in considering potential dielectric heating applications. General principles are discussed as they relate to dielectric properties of materials and energy absorption from radio-frequency and microwave electric fields. Measurement principles and techniques for determining the dielectric properties

Stuart O. Nelson

2006-01-01

450

Electrical stability of metal/low dielectric constant material systems  

NASA Astrophysics Data System (ADS)

In order to boost the performance of future generation silicon integrated circuits, new materials with lower dielectric constant (kappa) are under evaluation to replace traditional SiO2 as on-chip inter-layer dielectrics (ILDs). The goal of this thesis has been to investigate the intrinsic electrical stability and metal penetration resistance of a variety of low kappa materials: fluorinated silica glass (FSG), polyparaxylylene-N (parylene-N), polyarylether (PAE) and hybrid organosiloxane polymer (HOSP). Emphasis was placed on fundamental understanding of the factors controlling the electrical properties of different metal/low kappa dielectric systems. Traditionally, metal ion penetration is studied using Bias Temperature Stressing (BTS) with Capacitance-Voltage (C-V) measurement. In this work, an alternative technique, Triangular Voltage Sweep (TVS), was also adopted to provide insight into metal penetration behavior. Surprisingly, aluminum ion penetration into oxygen containing polymers such as PAE and HOSP was detected, and was in contrast to the stability of the Al/SiO2 system. Platinum was demonstrated as a viable control for metal drift studies in such polymers, as no platinum ion penetration was detected. Among the blanket dielectrics, the number of copper ions detected was lowest in HOSP, demonstrating its promise for ILD applications. Experimentation with a variety of metals led to the result that ion penetration behavior in HOSP showed the trend Pt < Cu < Ta < Al. This trend indicated that metal penetration increases with metal ionization and oxidation tendency. Plasma modification of HOSP by converting its surface to a thin intrinsic dielectric barrier resembling SiO2 dramatically reduced aluminum ion penetration in HOSP. Surface modification is therefore a powerful strategy to realize the future requirement of ultra-thin barriers. The impact of on-chip integration on electrical stability was also studied. Copper ions were detected along fast diffusion paths in an integrated FSG due to barrier failure and processing-related copper contamination. The results from all the various novel dielectrics clearly establish that metal/dielectric interactions induced by thermal and electrical treatments are very unlike those observed in metal/SiO2 systems. Careful evaluation is required to elucidate the metal penetration mechanism as it is influenced by surface chemistry, metal ionization and chemical reactivity, and bulk dielectric structure or composition.

Mallikarjunan, Anupama

451

Magneto-optical properties of ultrathin ferromagnetic films  

SciTech Connect

The surface magneto-optic Kerr effect (SMOKE) has been used to explore the properties of ultrathin ferromagnetic films. The ultrathin regime corresponds to thicknesses less than the depth penetration of light and includes the monolayer range. The ultrathin regime possesses unique magneto-optic properties: the Kerr rotation and ellipticity, in general, behave differently than in the thick film limit. Measurements and simulation in the longitudinal geometry for bcc Fe on Au(100) provide a dramatic example of the metallic reflector enhancement effect due to the nonmagnetic Au underlayer. The rotation enhancement is accompanied by a high reflectivity, as opposed to being at the expense of the reflectivity. Measurements in both polar and longitudinal geometries for epitaxially-stabilized fcc Fe films grown on Cu(100) and Pd(100) indicate the presence of perpendicular surface anisotropy, which suggests new approaches to realizing vertical data-storage media. 31 refs., 7 figs.

Bader, S.D.; Moog, E.R.; Liu, C.; Zak, J.

1989-04-01

452

Single-step synthesis of layered double hydroxides ultrathin nanosheets.  

PubMed

A novel single-step approach was developed to prepare large-scale MgAl-LDHs ultrathin nanosheets. The key point of the successful realization was that we employed a high concentration of H(2)O(2). Oxygen molecules, derived from in situ decomposition of H(2)O(2), were speculated to be the decisive factor leading to complete separation of LDHs layers. The ultrathin nanosheets were characterized by XRD, TEM, AFM, FT-IR, and TG-DSC. The results indicated that the thickness of these nanosheets was about 1.44 nm, which was almost in perfect agreement with the theoretical thickness of two LDHs layers. From the TG-DSC curves, the weight loss of these exfoliated MgAl-LDHs ultrathin nanosheets at 500°C was 18.5%, which was much smaller compared to the 32.3% weight loss of unexfoliated MgAl-LDHs. PMID:22304932

Yan, Yanxia; Liu, Qi; Wang, Jun; Wei, Jinbo; Gao, Zan; Mann, Tom; Li, Zhanshuang; He, Yang; Zhang, Milin; Liu, Lianhe

2012-04-01

453

Dispersion characteristic of ultrathin terahertz planar lenses based on metasurface  

NASA Astrophysics Data System (ADS)

Terahertz (THz) radiation has attached a lot of attention due to its potential applications. The smart optical components will greatly boost the application of the THz technology. Ultrathin planar lenses which can greatly reduce the thickness of the components are designed and fabricated in the THz region based on the metasurface. The dispersion characteristic of this kind of ultrathin planar lenses is systematically investigated. It is demonstrated that the focal lengths of the proposed lenses become shorter with the wavelength of the illuminating light increasing. Moreover, the ultrathin planar lenses perform a good focusing characteristic over a broad wavelength range. The results help us to further understand the optical properties of the lenses based on the metasurface and provide a considerable important reference for its future applications in miniaturization and integration of the THz system.

Hu, Dan; Moreno, Gabriel; Wang, Xinke; He, Jingwen; Chahadih, Abdallah; Xie, Zhenwei; Wang, Bo; Akalin, Tahsin; Zhang, Yan

2014-07-01

454

Swelling of ultrathin crosslinked polyamide water purification membranes  

NASA Astrophysics Data System (ADS)

Polyamide (PA) ultrathin films represent the state-of-the-art nanofiltration and reverse osmosis membranes used in water desalination. The performance of these materials, such as permselectivity, is intimately linked with extent of swelling of the PA network. Thus, quantifying their swelling behavior would be a useful and simple route to understanding the specific network structural parameters that control membrane performance. In this work, we measure the swelling behavior of PA ultrathin films using X-ray reflectivity as a function of water hydration. By applying the Flory-Rehner theory used to describe the swelling behavior of polymer networks, we quantify the PA network properties including Flory interaction parameter and the monomer units between crosslinks. Finally, we demonstrate application of this measurement approach for characterizing the network properties of different types of PA ultrathin films relevant to water purification and discuss the relationship between network and transport properties.