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1.
Nanodots and microwires of ZrO_2 grown on LaAlO_3 by photo-assisted metal–organic chemical vapor deposition
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ZrO_2 nanodots are successfully prepared on LaAlO_3(LAO)(100) substrates by photo-assisted metal-organic chemical vapor deposition(MOCVD). It is indicated that the sizes and densities of ZrO_2 nanodots are controllable by modulating the growth temperature, oxygen partial pressure, and growth time. Meanwhile, the microwires are observed on the surfaces of substrates. It is found that there is an obvious competitive relationship between the nanodots and the microwires. In a growth temperature range from 500℃ to 660℃, the microwires turn longest and widest at 600℃, but in contrast, the nanodots grow into the smallest diameter at 600℃. This phenomenon could be illustrated by the energy barrier, decomposition rate of Zr(tmhd)_4, and mobility of atoms. In addition, growth time or oxygen partial pressure also affects the competitive relationship between the nanodots and the microwires. With increasing oxygen partial pressure from 451 Pa to 75_2 Pa,the microwires gradually grow larger while the nanodots become smaller. To further achieve the controllable growth, the coarsening effect of ZrO_2 is modified by varying the growth time, and the experimental results show that the coarsening effect of microwires is higher than that of nanodots by increasing the growth time to quickly minimize ZrO_2 energy density. 相似文献
2.
《Current Applied Physics》2018,18(7):843-846
We grow atomically thin molybdenum ditelluride (MoTe2) films on a SiO2/Si substrate by means of metal–organic chemical vapor deposition (MOCVD). Our Raman spectroscopy measurements reveal the formation of 2H-phase MoTe2 films. Further, transmission electron microscopy and X-ray photoelectron spectroscopy studies indicate a three-atomic-layer structure and the surface element composition of MoTe2 films. In this study, we mainly focus on the influence of metal contacts attached to the films on their electrical performance. We fabricate 2H-phase-MoTe2-based field-effect transistors (FETs) with various metal contacts such as titanium/gold, nickel and palladium, which present p-type semiconductor properties. We also examine the influence of the work functions of the contact metals on the electrical properties of three-atomic-layer-MoTe2-based FET devices. For a p-type MoTe2 semiconductor, higher work functions of the contact metals afford narrower Schottky barrier heights (SBHs) and eventually highly efficient carrier injection through the contacts. 相似文献
3.
Lee Ming-Kwei Yen Chih-Feng Chiu Shih-Chen 《Applied Physics A: Materials Science & Processing》2011,104(4):1175-1180
The electrical characteristics of thin TiO2 films prepared by metal–organic chemical vapor deposition grown on a p-type InP substrate were studied. For a TiO2 film of 4.7 nm on InP without and with ammonium sulfide treatment, the leakage currents are 8.8×10−2 and 1.1×10−4 A/cm2 at +2 V bias and 1.6×10−1 and 8.3×10−4 A/cm2 at −2 V bias. The lower leakage currents of TiO2 with ammonium sulfide treatment arise from the improvement of interface quality. The dielectric constant and effective oxide
charge number density are 33 and 2.5×1013 cm2, respectively. The lowest mid-gap interface state density is around 7.6×1011 cm−2 eV−1. The equivalent oxide thickness is 0.52 nm. The breakdown electric field increases with decreasing thickness in the range
of 2.5 to 7.6 nm and reaches 9.3 MV/cm at 2.5 nm. 相似文献
4.
High-crystalline GaSb epitaxial films grown on GaAs(001) substrates by low-pressure metal–organic chemical vapor deposition
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Orthogonal experiments of Ga Sb films growth on Ga As(001)substrates have been designed and performed by using a low-pressure metal–organic chemical vapor deposition(LP-MOCVD)system.The crystallinities and microstructures of the produced films were comparatively analyzed to achieve the optimum growth parameters.It was demonstrated that the optimized Ga Sb thin film has a narrow full width at half maximum(358 arc sec)of the(004)ω-rocking curve,and a smooth surface with a low root-mean-square roughness of about 6 nm,which is typical in the case of the heteroepitaxial single-crystal films.In addition,we studied the effects of layer thickness of Ga Sb thin film on the density of dislocations by Raman spectra.It is believed that our research can provide valuable information for the fabrication of high-crystalline Ga Sb films and can promote the integration probability of mid-infrared devices fabricated on mainstream performance electronic devices. 相似文献
5.
Mid-gap photoluminescence and magnetic properties of GaMnN films grown by metal–organic chemical vapor deposition
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Metal-organic chemical vapor deposition (MOCVD) grown ferromagnetic GaMnN films are investigated by photo- luminescence (PL) measurement with a mid-gap excitation wavelength of 405 nm. A sharp PL peak at 1.8 eV is found and the PL intensity successively decreases with the addition of Mn, in which the Mn concentration of sample A is below 1% ([Mn]A =0.75%) but its PL intensity is stronger than other samples'. The 1.8-eV PL peak is attributed to the recombination of electrons in the t2 state of the neutral Mn3+ acceptor with holes in the valence band. With Mn concentration increasing, the intensity of the PL peak decreases and the magnetic increment reduces in our samples. The correlation between the PL peak intensity and ferromagnetism of the samples is discussed in combination with the experimental results. 相似文献
6.
Effect of InxGal-xN "continuously graded" buffer layer on InGaN epilayer grown by metalorganic chemical vapor deposition
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In this paper we report on the effect of an lnxGal xN continuously graded buffer layer on an InGaN epilayer grown on a GaN template. In our experiment, three types of buffer layers including constant composition, continuously graded composition, and the combination of constant and continuously graded composition are used. Surface morphologies, crystalline quality, indium incorporations, and relaxation degrees of InGaN epilayers with different buffer layers are investigated. It is found that the InxGa1-xN continuously graded buffer layer is effective to improve the surface morphology, crystalline quality, and the indium incorporation of the InGaN epilayer. These superior characteristics of the continuously graded buffer layer can be attributed to the sufficient strain release and the reduction of dislocations. 相似文献
7.
8.
Observation of positive and small electron affinity of Si-doped AlN films grown by metalorganic chemical vapor deposition on n-type 6H–SiC
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We have investigated the electron affinity of Si-doped AlN films(N_(Si)= 1.0 × 10~(18)–1.0 × 10_(19)cm~(-3)) with thicknesses of 50, 200, and 400 nm, synthesized by metalorganic chemical vapor deposition(MOCVD) under low pressure on the ntype(001)6H–SiC substrates. The positive and small electron affinity of AlN films was observed through the ultraviolet photoelectron spectroscopy(UPS) analysis, where an increase in electron affinity appears with the thickness of AlN films increasing, i.e., 0.36 eV for the 50-nm-thick one, 0.58 eV for the 200-nm-thick one, and 0.97 e V for the 400-nm-thick one.Accompanying the x-ray photoelectron spectroscopy(XPS) analysis on the surface contaminations, it suggests that the difference of electron affinity between our three samples may result from the discrepancy of surface impurity contaminations. 相似文献
9.
《Current Applied Physics》2002,2(3):205-211
The nucleation of copper (Cu) with (hfac)Cu(VTMS) organometallic precursor is investigated for Si, SiO2, TiN, and W2N substrates. As the deposition temperature is increased, the dominant growth mechanism is observed to change from the nucleation of Cu particles to the clustering of Cu nuclei around 180 °C independent of the employed substrates. It is also observed that the cleaning of substrate surfaces with the diluted HF solution improves the selectivity of Cu nucleation between TiN and SiO2 substrates. Dimethyldichlorosilane treatment is found to passivate the surface of TiN substrate, contrary to the generally accepted belief, when the TiN substrate is cleaned by H2O2 solution before the treatment. 相似文献
10.
V. Selvamanickam Y. Chen J. Xie Y. Zhang A. Guevara I. Kesgin G. Majkic M. Martchevsky 《Physica C: Superconductivity and its Applications》2009,469(23-24):2037-2043
(Gd,Y)Ba2Cu3Ox tapes have been fabricated by metal organic chemical vapor deposition (MOCVD) with Zr-doping levels of 0–15 mol.% and Ce doping levels of 0–10 mol.% in 0.4 μm thick films. The critical current density (Jc) of Zr-doped samples at 77 K, 1 T applied in the orientation of H 6 c is found to increase with Zr content and shows a maximum at 7.5% Zr doping. The 7.5% Zr-doped sample exhibits a critical current density (Jc) of 0.95 MA/cm2 at H 6 c which is more than 70% higher than the Jc of the undoped sample. The peak in Jc at H 6 c is 83% of that at H 6 a–b in the 7.5% Zr-doped sample which is more than twice as that in the undoped sample. Superconducting transition temperature (Tc) values as high as about 89 K have been achieved in samples even with 15% Zr and 10% Ce. Ce-doped samples with and without Ba compensation are found to exhibit substantially different Jc values as well as angular dependence characteristics. 相似文献
11.
The initial growth stage of GaSb on GaAs(001) by low pressure metal–organic chemical vapor deposition(MOCVD)is investigated. The dependence of the nucleation on growth temperature, growth pressure, and vapor V/III ratio is studied by means of atomic force microscopy. The nucleation characteristics include the island density, size, and size uniformity distribution. The nucleation mechanism is discussed by the effects of growth temperature, growth pressure, and vapor V/III ratio on the density, size, and size uniformity of GaSb islands. With the growth temperature increasing from 500℃ to610℃ and the growth pressure increasing from 50 mbar to 1000 mbar(1 mbar = 105Pa), the island density first increases and then decreases; with the V/III ratio increasing from 0.5 to 3, the trend is contrary. 相似文献
12.
Optical properties of 1.3-μm InAs/GaAs quantum dots grown by metal organic chemical vapor deposition
The optical properties of self-assembled InAs quantum dots (QDs) on GaAs substrate grown by metalorganic chemical vapor deposition (MOCVD) are reported. Photoluminescence (PL) measurements prove the good optical quality of InAs QDs, which axe achieved using lower growth temperature and higher InAs coverage. At room temperature, the ground state peak wavelength of PL spectrum and full-width at half-maximum (FWHM) are 1305 nm and 30 meV, respectively, which are obtained as the QDs are finally capped with 5-nm In0.06Ga0.94As strain-reducing layer (SRL). The PL spectra exhibit two emission peaks at 1305 and 1198 nm, which correspond to the ground state (GS) and the excited state (ES) of the QDs, respectively. 相似文献
13.
In this work,(-201) β-Ga_2O_3 films are grown on GaN substrate by metal organic chemical vapor deposition(MOCVD). It is revealed that the β-Ga_2O_3 film grown on GaN possesses superior crystal quality, material homogeneity and surface morphology than the results of common heteroepitaxial β-Ga_2O_3 film based on sapphire substrate. Further, the relevance between the crystal quality of epitaxial β-Ga_2O_3 film and the β-Ga_2O_3/GaN interface behavior is investigated. Transmission electron microscopy result indicates that the interface atom refactoring phenomenon is beneficial to relieve the mismatch strain and improve the crystal quality of subsequent β-Ga_2O_3 film. Moreover, the energy band structure of β-Ga_2O_3/GaN heterostructure grown by MOCVD is investigated by X-ray photoelectron spectroscopy and a large conduction band offset of 0.89 eV is obtained. The results in this work not only convincingly demonstrate the advantages of β-Ga_2O_3 films grown on GaN substrate, but also show the great application potential of MOCVD β-Ga_2O_3/GaN heterostructures in microelectronic applications. 相似文献
14.
Effect of In_x Ga_(1-x )N “continuously graded” buffer layer on InGaN epilayer grown by metalorganic chemical vapor deposition
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In this paper we report on the effect of an In x Ga1-x N continuously graded buffer layer on an InGaN epilayer grown on a GaN template.In our experiment,three types of buffer layers including constant composition,continuously graded composition,and the combination of constant and continuously graded composition are used.Surface morphologies,crystalline quality,indium incorporations,and relaxation degrees of InGaN epilayers with different buffer layers are investigated.It is found that the In x Ga1-x N continuously graded buffer layer is effective to improve the surface morphology,crystalline quality,and the indium incorporation of the InGaN epilayer.These superior characteristics of the continuously graded buffer layer can be attributed to the sufficient strain release and the reduction of dislocations. 相似文献
15.
《Current Applied Physics》2014,14(7):954-959
We report the design and fabrication of an integrated Mach–Zehnder interferometric (MZI) biochip based on silicon oxynitride layers deposited with a plasma-enhanced chemical vapor deposition (PECVD) process. A rib waveguide for an integrated MZI sensor has been designed to have a high surface sensitivity and a single-mode behavior by using an effective index method. The integrated MZI chip operating at 637 nm is fabricated via conventional photolithography and reactive ion etching. As a biosensor application, the real-time and label-free detection of the covalent immobilization and hybridization of DNA strands is performed and verified with this device. 相似文献
16.
L.L. Ying Z.Y. Liu Y.M. Lu B. Gao F. Fan J.L. Liu C.B. Cai T. Thersleff S. Engel R. Hühne B. Holzapfel 《Physica C: Superconductivity and its Applications》2009,469(7-8):288-292
In the present work, La2Zr2O7 (LZO) buffer layers were deposited using pulsed laser deposition (PLD) on various metallic substrates including epitaxial pure Ni on a LaAlO3 (LAO) substrate as well as highly textured Ni–5 at.%W tapes. It is shown that the LZO deposited on pure Ni-buffered LAO exhibits a mixed orientation while LZO on Ni–5 at.%W grows epitaxially. This difference may be explained by the existence of a sulphur superstructure on the surface of Ni–5 at.%W tapes, promoting the epitaxial (0 0 l) nucleation of seed layers. Highly textured YBa2Cu3O7?δ layers were prepared either by using a single buffer layer of LZO or bilayer buffers of CeO2/LZO on Ni–5 at.%W. The superconducting transition temperature (Tc) increases with the LZO thickness, reaching a value of 90 K with a very narrow transition width (1.5 K) for 240 nm thick LZO layers. Inductive Jc measurements at 77 K in self-field show a value of about 0.96 MA/cm2 for the thickest LZO layers, which is comparable to the value observed on standard buffer architectures such as CeO2/YSZ/Y2O3. 相似文献
17.
《Current Applied Physics》2015,15(4):473-478
In this work, graphene oxide–cuprous oxide (GO–Cu2O) composite films were grown on fluorine-doped tin oxide substrates by electrochemical deposition. We investigated the effects of the annealing temperature on the morphological, structural, optical and photoelectrochemical (PEC) properties of GO–Cu2O composite films. As a result, our work shows that while GO–Cu2O composite films exhibit the highest XRD (111) peak intensity at 300 °C sample, the highest photocurrent density value obtained was −4.75 mA/cm2 at 200 °C sample (using 0.17 V versus a reversible hydrogen electrode (RHE)). In addition, a reduction reaction at 300 °C sample was observed using XPS analysis from the shift in the O1s peak in addition to a weaker O1s peak intensity. 相似文献
18.
We prepared Al2O3 films by laser chemical vapor deposition (LCVD) using a diode laser and aluminum acetylacetonate (Al(acac)3) precursors and investigated the effects of laser power (PL), deposition temperature (Tdep), and total pressure (Ptot) in a reaction chamber on the crystal phase, microstructure, and deposition rate (Rdep). An amorphous phase was obtained at PL = 50 W, whereas an α-phase was obtained at PL > 100 W. At PL = 150 and 200 W (1 0 4)- and (0 1 2)-oriented α-Al2O3 films were obtained, respectively. The Rdep of α-Al2O3 films increases with decreasing PL and Ptot. Single-phase α-Al2O3 film was obtained at Tdep = 928 K, which is about 350 K lower than that obtained by conventional thermal CVD using Al(acac)3 precursor. 相似文献
19.
E. Piscopiello A. Rosenauer A. Passaseo E. H. Montoya Rossi G. Van Tendeloo 《哲学杂志》2013,93(32):3857-3870
Using quantitative high-resolution transmission electron microscopy we studied the chemical morphology of wetting layers in In x Ga1? x As/GaAs quantum dot structures which were optimized for applications to optical devices operating around 1.3?µm. The samples are grown by low-pressure metal–organic chemical vapour deposition on GaAs substrates. The In concentration profiles of the wetting layers are evaluated with the composition evaluation by lattice fringe analysis method. The profiles reveal a clear signature of segregation. A fit of the profiles with the Muraki et al. model for segregation reveals a segregation efficiency R?=?0.65?±?0.05 at the growth temperature of 550°C, which is significantly lower than segregation efficiencies observed in samples grown by molecular beam epitaxy at similar temperatures. 相似文献
20.
Laser-induced voltage effects in CaaCoaO9 thin films on tilted LaAlO3(001) substrates grown by chemical solution deposition
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Wang Shu-Fang Chen Ming-Jing Zhao Shu-Rui Chen Jing-Chun He Li-Ping Yu Wei Wang Jiang-Long Fu Guang-Sheng 《中国物理 B》2010,(10):441-444
Laser-induced voltage effects in c-axis oriented Ca3Co4O9 thin films have been studied with samples fabricated on 10°tilted LaAIO3 (001) substrates by a simple chemical solution deposition method. An open-circuit voltage with a rise time of about 10 ns and full width at half maximum of about 28 ns is detected when the film surface is irradiated by a 308-nm laser pulse with a duration of 25 ns. Besides, opemcircuit voltage signals are also observed when the film surface is irradiated separately by the laser pulses of 532 nm and 1064 nm. The results indicate that Ca3Co4O9 thin films have a great potential application in the wide range photodetctor from the ultraviolet to near infrared regions. 相似文献