scholarly journals Statistical Analysis of Uniform Switching Characteristics of Ta2O5-Based Memristors by Embedding In-Situ Grown 2D-MoS2 Buffer Layers

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6275
Author(s):  
Soeun Jin ◽  
Jung-Dae Kwon ◽  
Yonghun Kim
Keyword(s):  
Buffer Layer ◽  
Chemical Vapor ◽  
Metal Electrode ◽  
Thin Layers ◽  
Buffer Layers ◽  
Switching Operation ◽  
Computing Device ◽  
Switching Characteristics ◽  
Highly Uniform ◽  
Switching Layer

A memristor based on emerging resistive random-access memory (RRAM) is a promising candidate for use as a next-generation neuromorphic computing device which overcomes the von Neumann bottleneck. Meanwhile, due to their unique properties, including atomically thin layers and surface smoothness, two-dimensional (2D) materials are being widely studied for implementation in the development of new information-processing electronic devices. However, inherent drawbacks concerning operational uniformities, such as device-to-device variability, device yield, and reliability, are huge challenges in the realization of concrete memristor hardware devices. In this study, we fabricated Ta2O5-based memristor devices, where a 2D-MoS2 buffer layer was directly inserted between the Ta2O5 switching layer and the Ag metal electrode to improve uniform switching characteristics in terms of switching voltage, the distribution of resistance states, endurance, and retention. A 2D-MoS2 layered buffer film with a 5 nm thickness was directly grown on the Ta2O5 switching layer by the atomic-pressure plasma-enhanced chemical vapor deposition (AP-PECVD) method, which is highly uniform and provided a superior yield of 2D-MoS2 film. It was observed that the switching operation was dramatically stabilized via the introduction of the 2D-MoS2 buffer layer compared to a pristine device without the buffer layer. It was assumed that the difference in mobility and reduction rates between Ta2O5 and MoS2 caused the narrow localization of ion migration, inducing the formation of more stable conduction filament. In addition, an excellent yield of 98% was confirmed while showing cell-to-cell operation uniformity, and the extrinsic and intrinsic variabilities in operating the device were highly uniform. Thus, the introduction of a MoS2 buffer layer could improve highly reliable memristor device switching operation.

Epitaxial GaN Layer Growth Using Nitrogen Enriched TiN Buffer Layers

2006 ◽  
Vol 916 ◽  
Author(s):  
Kazuhiro Ito ◽  
Yu Uchida ◽  
Sang-jin Lee ◽  
Susumu Tsukimoto ◽  
Yuhei Ikemoto ◽  
...  
Keyword(s):  
Buffer Layer ◽  
Light Emission ◽  
Chemical Vapor ◽  
Nucleation Site ◽  
Layer Growth ◽  
Buffer Layers ◽  
Organic Chemical ◽  
Nitrogen Enrichment ◽  
Threading Dislocation ◽  
Sapphire Substrates

AbstractAbout 20 years ago, the discovery of an AlN buffer layer lead to the breakthrough in epitaxial growth of GaN layers with mirror-like surface, using a metal organic chemical vapor deposition (MOCVD) technique on sapphire substrates. Since then, extensive efforts have been continued to develop a conductive buffer layer/substrate for MOCVD-grown GaN layers to improve light emission of GaN light-emitting diodes. In the present study, we produced MOCVD-grown, continuous, flat epitaxial GaN layers on nitrogen enriched TiN buffer layers with the upper limit of the nitrogen content of TiN deposited at room temperature (RT) on sapphire substrates. It was concluded that the nitrogen enrichment would reduce significantly the TiN/GaN interfacial energy. The RT deposition of the TiN buffer layers suppresses their grain growth during the nitrogen enrichment and the grain size refining must increase nucleation site of GaN. In addition, threading dislocation density in the GaN layers grown on TiN was much lower than that in the GaN layers grown on AlN.

Characterization of Gan/Sapphire Interface and the Buffer Layer by TEM/AFM

2001 ◽  
Vol 7 (S2) ◽  
pp. 330-331
Author(s):  
B. Shea ◽  
Q. Sun-Paduano ◽  
D. F. Bliss ◽  
M. C. Callahan ◽  
C. Sung
Keyword(s):  
Buffer Layer ◽  
Gas Flow ◽  
Chemical Vapor ◽  
Wide Band ◽  
Buffer Layers ◽  
Organic Chemical ◽  
Wide Band Gap ◽  
Tem Analysis ◽  
Flow Rates ◽  
Device Applications

Interest in wide band gap III-V nitride semiconductor devices is increasing for optoelectronic and microelectronic device applications. to ensure the highest quality, TEM analysis can characterize the substrate and buffer layer interface. Measurements taken by TEM reveal the density of dislocations/cm2 and the orientation of Burger's vectors. This information allows for changes to be made in deposition rates, temperatures, gas flow rates, and other parameters during the processing.The GaN/sapphire samples grown at AFRL were produced in two consecutive steps, first to provide a thin buffer layer, and the other to grow a lum thick epitaxial film. Both growth steps were prepared using metallic organic chemical vapor deposition (MOCVD) in a vertical reactor. Buffer layers were prepared using a range of temperatures from 525 to 535°C and with a range of flow rates and pressures in order to optimize the nucleation conditions for the epitaxial films.

Fabrication of Diamond Films on Cu Metal Substrates with Buffers (SiC or MoSi2) by Hot Filament Chemical Vapor Deposition

2014 ◽  
Vol 936 ◽  
pp. 276-281
Author(s):  
Qi Zhao ◽  
Ming Jiang Dai ◽  
Di Tan ◽  
Chun Bei Wei ◽  
Wan Qi Qiu ◽  
...  
Keyword(s):  
Buffer Layer ◽  
Diamond Film ◽  
Copper Substrate ◽  
Diamond Films ◽  
Chemical Deposition ◽  
Chemical Vapor ◽  
Metal Substrate ◽  
Buffer Layers ◽  
Laser Raman ◽  
Hot Filament

Diamond films were grown by hot filament chemical deposition (HFCVD) on Cu metal substrate with two different buffer layers (SiC or MoSi2) synthesized by using magnetron sputtering technique. The components of films were investigated using X-ray diffraction (XRD) and laser Raman spectrum, and the surface morphology and structure were observed with scanning electron microscopy (SEM). Film adherence was investigated by micro-indentation. The results showed that the diamond films were successfully grown on Cu metal substrate with two different buffer layers. There were cracks on diamond film grown on 3µm SiC buffer layer and some SiC crystal whiskers were observed. Dense diamond films with bad adhesion were observed on 22µm MoSi2 buffered copper substrate. MoSi2 made chemical reaction with CH4 and produced MoC and Mo5Si3 on the process of HFCVD. Conclusion: the 3µm buffer layer of SiC can’t help deposit no cracking diamond film; the 22µm buffer layer of MoSi2 is helpful for depositing good diamond film, but can’t effectively improve the bond strength between diamond film and copper substrate.

Silicon Nanowire Electromechanical Switch for Logic Device Application

2007 ◽  
Vol 1018 ◽  
Author(s):  
Qiliang Li ◽  
Sang-Mo Koo ◽  
Monica D. Edelstein ◽  
John S. Suehle ◽  
Curt A. Richter
Keyword(s):  
Silicon Nanowires ◽  
Silicon Nanowire ◽  
Chemical Vapor ◽  
Metal Electrode ◽  
Subthreshold Slope ◽  
Logic Device ◽  
Metal Electrodes ◽  
Device Application ◽  
Switching Characteristics

AbstractIn this paper, we have reported the fabrication and characterization of nanowire electromechanical switches consisting of chemical-vapor-deposition grown silicon nanowires suspended over metal electrodes. The devices operate as transistors with the suspended part of the nanowire bent to touch metal electrode via electromechanical force by applying voltage. The reversible switching, large on/off current ratio, small subthreshold slope and low switching energy compared to current CMOSFET make the switches very attractive for logic device application. In addition, we have developed a physical model to investigate the switching characteristics and extract the material properties.

scholarly journals High Quality GaAs Epilayers Grown on Si Substrate Using 100 nm Ge Buffer Layer

2016 ◽  
Vol 2016 ◽  
pp. 1-5 ◽  
Author(s):  
Wei-Cheng Kuo ◽  
Hung-Chi Hsieh ◽  
Wu Chih-Hung ◽  
Huang Wen-Hsiang ◽  
Chien-Chieh Lee ◽  
...  
Keyword(s):  
Buffer Layer ◽  
High Efficiency ◽  
Electron Cyclotron Resonance ◽  
Low Cost ◽  
Chemical Vapor ◽  
Buffer Layers ◽  
High Quality ◽  
Tandem Solar Cells ◽  
Hydrogen Flow ◽  
Transmission Electron

We present high quality GaAs epilayers that grow on virtual substrate with 100 nm Ge buffer layers. The thin Ge buffer layers were modulated by hydrogen flow rate from 60 to 90 sccm to improve crystal quality by electron cyclotron resonance chemical vapor deposition (ECR-CVD) at low growth temperature (180°C). The GaAs and Ge epilayers quality was verified by X-ray diffraction (XRD) and spectroscopy ellipsometry (SE). The full width at half maximum (FWHM) of the Ge and GaAs epilayers in XRD is 406 arcsec and 220 arcsec, respectively. In addition, the GaAs/Ge/Si interface is observed by transmission electron microscopy (TEM) to demonstrate the epitaxial growth. The defects at GaAs/Ge interface are localized within a few nanometers. It is clearly showed that the dislocation is well suppressed. The quality of the Ge buffer layer is the key of III–V/Si tandem cell. Therefore, the high quality GaAs epilayers that grow on virtual substrate with 100 nm Ge buffer layers is suitable to develop the low cost and high efficiency III–V/Si tandem solar cells.

scholarly journals New Technique for Sublimation Growth of AlN Single Crystals

2001 ◽  
Vol 6 ◽  
Author(s):  
Y. Shi ◽  
B. Liu ◽  
Lianghong Liu ◽  
J.H. Edgar ◽  
E.A. Payzant ◽  
...  
Keyword(s):  
Buffer Layer ◽  
Crack Density ◽  
Chemical Vapor ◽  
Alloy Film ◽  
Buffer Layers ◽  
New Technique ◽  
Organic Chemical ◽  
Aln Film ◽  
Aln Buffer ◽  
Sublimation Growth

Single crystalline platelets of aluminum nitride (AlN) were successfully grown by a new technique. It consists of (1) depositing an AlN buffer layer on a SiC substrate by metal organic chemical vapor deposition (MOCVD) below 1100°C, (2) forming an (AlN)x(SiC)1−x alloy film on the AlN film by condensing vapors sublimated at a temperature of 1800°C from a source mixture of AlN-SiC powders, followed by (3) condensing vapors sublimated from a pure AlN source (at 1800°C). The necessity of the first two steps for the successful AlN sublimation growth on SiC substrate was illustrated by the initial nucleation studies of alloys on SiC substrates with and without MOCVD AlN buffer layers: an AlN MOCVD buffer layer leads to continuous, single grain growth mode; The (AlN)x(SiC)1−x alloy film reduces the crack density because its thermal expansion coefficient is intermediate between SiC and AlN. X-ray diffraction (XRD) and Raman spectroscopy studies indicated the high quality of the AlN single crystal.

scholarly journals Effect of Employing Chromium as a Buffer Layer on the Crystallinity of Hexagonal Boron Nitride Films Grown by LPCVD

2021 ◽  
Author(s):  
Xi Chen ◽  
Kairan Luan ◽  
Wenbo Zhang ◽  
Xiuhuan Liu ◽  
Jihong Zhao ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Buffer Layer ◽  
Growth Temperature ◽  
Hexagonal Boron Nitride ◽  
Chemical Vapor ◽  
Annealing Process ◽  
Pressure Chemical ◽  
Switching Characteristics

Abstract Using chromium (Cr), which was deposited by radio frequency magnetron sputtering, as a buffer layer for synthesizing high-quality hexagonal boron nitride (hBN) films by low-pressure chemical vapor deposition (LPCVD) was demonstrated. The effect of growth temperature and annealing process on the quality of the Cr buffer layer was investigated. The characterization of the dependence of hBN film quality on growth temperature, substrate, and annealing process was discussed. All evidence shows that using a Cr buffer layer can significantly improve the crystalline quality of hBN. A DUVPD based on hBN film using Cr as the bottom electrode was fabricated with a small leakage current. The photocurrent is 3.5 nA at a bias of 500 V, and it exhibits good switching characteristics.

Simulations of Buffer Layers in a-Si:H Thin Film Solar Cells Deposited with an Expanding Thermal Plasma

2003 ◽  
Vol 762 ◽  
Author(s):  
A.M.H.N. Petit ◽  
M. Zeman ◽  
R.A.C.M.M. van Swaaij ◽  
M.C.M. van de Sanden
Keyword(s):  
Solar Cell ◽  
Electric Field ◽  
Buffer Layer ◽  
Thermal Plasma ◽  
Defect Density ◽  
Chemical Vapor ◽  
Buffer Layers ◽  
High Deposition Rate ◽  
Solar Cell Performance ◽  
Plasma Chemical Vapor Deposition

AbstractWith an Expanding Thermal Plasma Chemical Vapor Deposition system (ETP-CVD), solar grade amorphous silicon (a-Si:H) can be deposited at high deposition rate (> 2 nm/s). We think that during the first stage of deposition, a material is grown with a higher defect density than the rest of the bulk creating a defect-rich layer (DRL). Therefore we analyzed, by the means of simulations, the influence of the position of the DRL on the performance of a p-i-n a-Si:H solar cell when moved from the p-i towards the i-n interface and as a function of its thickness. We investigate the effect of a buffer layer in between the p- and the i-layer on the external parameters of the solar cell. The presence of a buffer layer increases the electric field near the p-i interface, which leads to a higher collection of free charge carriers at the interface, although the electric field is then diminished deeper in the bulk. It appears that 10 nm thick buffer layer is sufficient to improve the performance. In case no buffer layer is applied, recombination losses at the p-i interface diminish the performance of the solar cell. We also observe that an increase of the DRL thickness results in a reduction of the solar-cell performance, which is more pronounced when the DRL is located in the region close to the p-i interface rather than close to the i-n interface.

Initial Stages of MOCVD Growth of Gallium Nitride Using a Multi-Step Growth Approach

1997 ◽  
Vol 468 ◽  
Author(s):  
J. T. Kobayashi ◽  
N. P. Kobayashi ◽  
P. D. Dapkus ◽  
X. Zhang ◽  
D. H. Rich
Keyword(s):  
Low Temperature ◽  
Buffer Layer ◽  
Chemical Vapor ◽  
Buffer Layers ◽  
Mocvd Growth ◽  
Initial Stage ◽  
Step Growth ◽  
Van Der Pauw ◽  
Growth Approach

ABSTRACTA multilayer buffer layer approach to GaN growth has been developed in which the thermal desorption and mass transport of low temperature buffer layer are minimized by deposition of successive layers at increased temperatures. High quality GaN with featureless surface morphology has been grown on (0001) sapphire substrate by metalorganic chemical vapor deposition using this multilayer buffer layer approach. The lateral growth and coalescence of truncated 3D islands (TTIs) nucleated on low temperature buffer layers at the initial stage of overlayer growth is affected by the thickness of the final buffer layer on which nucleation of TTIs takes place. The effect of the thickness of this buffer layer on the quality of GaN is studied by using scanning electron microscopy, van der Pauw geometry Hall measurements and cathodoluminescence and an optimum value of 400Å is obtained.

{10} edge dislocations in YSZ films grown on (100)MgO by PLD

1994 ◽  
Vol 52 ◽  
pp. 530-531
Author(s):  
Jason R. Heffelfinger ◽  
C. Barry Carter
Keyword(s):  
Thin Films ◽  
Semiconductor Lasers ◽  
Vapor Deposition ◽  
Substrate Surface ◽  
Laser System ◽  
Average Energy ◽  
Target Material ◽  
Chemical Vapor ◽  
Buffer Layers ◽  
Organic Chemical

Yttria-stabilized zirconia (YSZ) is currently used in a variety of applications including oxygen sensors, fuel cells, coatings for semiconductor lasers, and buffer layers for high-temperature superconducting films. Thin films of YSZ have been grown by metal-organic chemical vapor deposition, electrochemical vapor deposition, pulse-laser deposition (PLD), electron-beam evaporation, and sputtering. In this investigation, PLD was used to grow thin films of YSZ on (100) MgO substrates. This system proves to be an interesting example of relationships between interfaces and extrinsic dislocations in thin films of YSZ.In this experiment, a freshly cleaved (100) MgO substrate surface was prepared for deposition by cleaving a lmm-thick slice from a single-crystal MgO cube. The YSZ target material which contained 10mol% yttria was prepared from powders and sintered to 85% of theoretical density. The laser system used for the depositions was a Lambda Physik 210i excimer laser operating with KrF (λ=248nm, 1Hz repetition rate, average energy per pulse of 100mJ).

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