Heteroepitaxial Growth Of ZnO Films BY PLD

1997 ◽  
Vol 474 ◽  
Author(s):  
R. D. Vispute ◽  
V. Talyansky ◽  
Z. Trajanovic ◽  
S. Choopun ◽  
M. Downes ◽  
...  
Keyword(s):  
Oxygen Pressure ◽  
Surface Region ◽  
Optical Quality ◽  
Degree Of Crystallinity ◽  
Zno Films ◽  
Heteroepitaxial Growth ◽  
Near Surface ◽  
Ion Channeling ◽  
Deposition Parameters ◽  
High Degree

ABSTRACTHere we present our recent work on the fabrication of high crystalline and optical quality ZnO films on sapphire (001) by pulsed laser deposition. The influence of deposition parameters such as the substrate temperature, oxygen pressure, laser fluence, and pulse repetition rate on the crystalline quality of ZnO layers has been studied. The Ω-rocking curve FWHM of the (002) peak for the films grown at 750°, oxygen pressure 10−5 Torr was 0.17°. The XRD-Ф scans studies revealed that the films were epitaxial with a 30° rotation of the unit cell with respect to the sapphire to achieve a low energy configuration for epitaxial growth. The high degree of crystallinity was confirmed by ion channeling technique providing a minimum Rutherford backscattering yield of 2–3% in the near surface region (-2000Å). The atomic force microscopy revealed smooth hexagonal faceting of the films. The optical absorption edge measured by UV-Visible spectroscopy was sharp at 383 nm. Excellent crystalline properties of these epi-ZnO/sapphire heterostractures are thus promising for III-V nitride heteroepitaxy.

Pulsed Laser Deposition of Highly Crystalline Gan Films on Sapphire

1997 ◽  
Vol 482 ◽  
Author(s):  
R. D. Vispute ◽  
V. Talyansky ◽  
S. Chupoon ◽  
R. Enck ◽  
T. Dahmas ◽  
...  
Keyword(s):  
Pulsed Laser Deposition ◽  
Pulsed Laser ◽  
Target Surface ◽  
Surface Region ◽  
Laser Deposition ◽  
Degree Of Crystallinity ◽  
X Ray Diffraction ◽  
Rocking Curve ◽  
Ion Channeling ◽  
High Degree

AbstractWe report high quality epitaxial growth of GaN film by pulsed laser deposition technique. In this method, a KrF pulsed excimer laser was used for ablation of a polycrystalline, stoichiometric GaN target. The ablated material was deposited on a substrate kept at a distance of ∼ 7 cm from the target surface and in an NH3 background pressure of 10−5 Torr and temperature of 750°C. The films (∼0.5 μm thick) grown on AIN buffered sapphire showed a x-ray diffraction rocking curve FWHM of 4–6 arc minutes. The ion channeling minimum yield in the surface region was ∼3% indicating a high degree of crystallinity. The optical band gap was found to be 3.4 eV. The epitaxial films were shiny, and the surface RMS roughness was ∼ 5–15 nm. The electrical resistivity of these films was in the range of 10−2–102 Ω-cm with a mobility in excess of 60 cm2V-1s−1 and carrier concentration of 1017–1019cm−3.

Heteroepitaxial Growth of Ba0.5Sr0.5TiO3/SrRuO3 on YSZ/Si by Off-Axis Sputtering

1994 ◽  
Vol 361 ◽  
Author(s):  
S.Y. Hou ◽  
J. Kwo ◽  
R.K. Watts ◽  
J.-Y. Cheng ◽  
R.J. Cava ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Degree Of Crystallinity ◽  
Heteroepitaxial Growth ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Dielectric Constant And Loss ◽  
Bst Films ◽  
High Degree ◽  
Room Temperature Dielectric Constant

ABSTRACTWe demonstrate an epitaxial heterostructure of Ba0.5Sr0.5 TiO3/SrRuO3/YSZ on Si for potential charge storage applications. The dielectric Ba0.5Sr0.5TiO3 (BST) and conductive oxide SrRuO3 are both grown (110) oriented on YSZ (100) buffered Si by 90° off-axis sputtering. These films showed a high degree of crystallinity with minimal interdiffusion at the interfaces as examined by X-ray diffraction, Rutherford backscattering spectroscopy, and cross-section transmission electron microscopy. The in-plane epitaxial alignment of the films is BST/SRO 〈111〉 // YSZ 〈110〉 with a four-fold degeneracy. The dielectric constant and loss tangent of the epi-BST films are 360 and 0.01 at 10 kHz. The leakage current density is < 4×10∼−7 A/cm2 at 1 V. The room temperature dielectric constant (ε) of the BST films shows a roll-off in the 1–10 MHz range. This is attributed to the existence of a series resistance in the measurement circuit, which likely arises from the SrRuO3 electrode.

Deposition of Low-Stress Encapsulants on InP and GaAs

1986 ◽  
Vol 75 ◽  
Author(s):  
U. K. Chakrabarti ◽  
S. J. Pearton ◽  
H. Barz ◽  
A. R. Vonneida ◽  
K. T. Short ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Secondary Ion Mass Spectrometry ◽  
Surface Region ◽  
Near Surface ◽  
Deposition Parameters ◽  
Direct Measurements ◽  
Dopant Redistribution ◽  
Doped Glass ◽  
Phosphorus Doped ◽  
Secondary Ion

AbstractAℓN deposited by D.C. triode sputtering and spin-on, phosphorus-doped glass (PSG) layers on GaAs and InP were investigated as encapsulants. These films have similar expansion coefficients to both GaAs and InP, minimizing the amount of strain induced in the near-surface region of the underlying wafer. We have quantified this effect by direct measurements of the stress in the films and by using secondary ion mass spectrometry profiling to measure the redistribution of Cr and Fe in encapsulated GaAs and InP respectively during high temperature processing. The dopant redistribution is considerably less for the AℓN and PSG films compared to the more conventional SiO2 and Si3N4 layers. The interaction of the films with the substrate at elevated temperatures is minimal as determined by Auger profiling and the electrical properties of the surface after removal of the encapsulants. The composition of the films remains essentially constant after annealing, as measured by Rutherford backscattering, and the thickness uniformity over large wafer diameters (2″) can be excellent with close control of the deposition parameters. The activation characteristics of low dose, Si-implanted layers in GaAs using either PSG or AℓN are comparable to those obtained using capless annealing or SiO2 or Si3N4 encapsulation.

scholarly journals Pulsed-laser-deposited AlN films for high-temperature SiC MIS devices

2000 ◽  
Vol 5 (S1) ◽  
pp. 591-597
Author(s):  
R. D. Vispute ◽  
A. Patel ◽  
K. Baynes ◽  
B. Ming ◽  
R. P. Sharma ◽  
...  
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Ohmic Contacts ◽  
Lattice Mismatch ◽  
Pulsed Laser ◽  
Surface Region ◽  
Degree Of Crystallinity ◽  
Ion Channeling ◽  
Cell Height ◽  
Mis Devices

We report on the fabrication of device-quality AlN heterostructures grown on SiC for high-temperature electronic devices. The AlN films were grown by pulsed laser deposition (PLD) at substrate temperatures ranging from 25 °C (room temperature) to 1000 °C. The as-grown films were investigated using x-ray diffraction, Rutherford backscattering specttroscopy, ion channeling, atomic force microscopy, and transmission electron microscopy. The AlN films grown above 700 °C were highly c-axis oriented with rocking curve FWHM of 5 to 6 arc-min. The ion channeling minimum yields near the surface region for the AlN films were ∼2 to 4%, indicating their high degree of crystallinity. TEM studies indicated that AlN films were epitaxial and single crystalline in nature with a large number of stacking faults as a results of lattice mismatch and growth induced defects. The surface roughness for the films was about 0.5 nm, which is close to the unit cell height of the AlN. Epitaxial TiN ohmic contacts were also developed on SiC, GaN, and AlN by in-situ PLD. Epitaxial TiN/AlN/SiC MIS capacitors with gate areas of 4 * 10−4 cm2 were fabricated, and high-temperature current-voltage (I-V) characteristics were studied up to 450 °C. We have measured leakage current densities of low 10−8 A/cm2 at room temperature, and have mid 10−3 A/cm2 at 450°C under a field of 2 MV/cm.

Pulsed-Laser-Deposited AlN Films for High-Temperature SiC MIS Devices

1999 ◽  
Vol 595 ◽  
Author(s):  
R. D. Vispute ◽  
A. Patel ◽  
K. Baynes ◽  
B. Ming ◽  
R. P. Sharma ◽  
...  
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Ohmic Contacts ◽  
Lattice Mismatch ◽  
Pulsed Laser ◽  
Surface Region ◽  
Degree Of Crystallinity ◽  
Ion Channeling ◽  
Cell Height ◽  
Mis Devices

AbstractWe report on the fabrication of device-quality AlN heterostructures grown on SiC for high-temperature electronic devices. The AlN films were grown by pulsed laser deposition (PLD) at substrate temperatures ranging from 25 °C (room temperature) to 1000 °C. The as-grown films were investigated using x-ray diffraction, Rutherford backscattering specttroscopy, ion channeling, atomic force microscopy, and transmission electron microscopy. The AlN films grown above 700 °C were highly c-axis oriented with rocking curve FWHM of 5 to 6 arc-min. The ion channeling minimum yields near the surface region for the AlN films were ∼2 to 4%, indicating their high degree of crystallinity. TEM studies indicated that AlN films were epitaxial and single crystalline in nature with a large number of stacking faults as a results of lattice mismatch and growth induced defects. The surface roughness for the films was about 0.5 nm, which is close to the unit cell height of the AlN. Epitaxial TiN ohmic contacts were also developed on SiC, GaN, and AlN by in-situ PLD. Epitaxial TiN/AlN/SiC MIS capacitors with gate areas of 4 * 10-4 cm2 were fabricated, and high-temperature current-voltage (I-V) characteristics were studied up to 450 °C. We have measured leakage current densities of low 10-8 A/cm2 at room temperature, and have mid 10-3 A/cm2 at 450°C under a field of 2 MV/cm.

Optimization of Laser Energy Fluence in Pulsed Laser Deposition of ZnO on Al2O3(0001)

2000 ◽  
Vol 648 ◽  
Author(s):  
W. Yang ◽  
R. D. Vispute ◽  
S. Choopun ◽  
R. P. Sharma ◽  
H. Shen ◽  
...  
Keyword(s):  
Laser Fluence ◽  
Laser Energy ◽  
Pulsed Laser ◽  
Optical Quality ◽  
Layer Growth ◽  
Zno Films ◽  
Energy Fluence ◽  
Ion Channeling ◽  
High Laser Fluence ◽  
Microscopy Techniques

AbstractThe effects of laser energy fluence on the growth of pulsed laser deposited ZnO thin films on c-plane sapphire substrates were systematically investigated by using x-ray diffraction, Rutherford backscattering spectrometry with ion channeling, and scanning electron microscopy techniques. Optical and electrical properties of the ZnO epilayers were characterized by using ultraviolet-visible transmission spectroscopy and Van der Pauw measurements, respectively. It was found that the laser fluence has strong effects on the crystalline, optical and electrical qualities of the ZnO films. At low laser fluence, ZnO film grows via 3D-island mode with low deposition rate, loss of Zn near the surface and particulates on top of the film. High laser fluence may also cause simultaneous multi-layer growth and the degradation of crystalline, electrical, and optical quality of the ZnO films. The optimal laser fluence window was found between 1.2J/cm2 and 2.5 J/cm2 for obtaining high quality ZnO films for optoelectronic applications. The dependence of laser fluence on the ZnO growth mode, surface morphology and electrical and optical properties is discussed.

Anisotropic Dry Etching of S1O2 on Si and its Impact on Surface and Near-Surface Properties of the Substrate.

1986 ◽  
Vol 68 ◽  
Author(s):  
G. S. Oehrlein ◽  
G. J. Coyle ◽  
J. C. Tsang ◽  
R. M. Tromp ◽  
J. G. Clabes ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Surface Properties ◽  
Surface Region ◽  
Dry Etching ◽  
High Concentration ◽  
Photoelectron Emission ◽  
Plasma Exposure ◽  
Near Surface ◽  
Ion Channeling ◽  
Fluorocarbon Film

AbstractIn the present paper structural and chemical changes which can occur in the surface and near-surface properties of the substrate during anisotropic dry etching of SiO2 on Si will be reviewed.Silicon specimens which had been etched in CF4/X%H2 (X≤40) have been characterized by X-ray photoelectron emission spectroscopy, He ion channeling, H profiling and Raman scattering techniques.Key results of our studies are summarized as follows: Plasma exposure of a Si surface leads to the deposition of a thin (≤50Å thick) C,F-film.A Si-carbide containing Si region is formed during RIE which is localized near the fluorocarbon-film/Si interface.The near-surface region (∼30–50Å) of the Si substrate is also heavily disordered as found by ion channeling and Raman scattering.A modified, less damaged Si region has been found in the case of hydrogen-based etching gases, which extends from about 30–50Å from the surface to a depth in extent of 250Å and contains a high concentration (∼ 5 at.%) of H as shown by hydrogen profiling techniques.From the observation of Si-H and Si-H2 vibrational modes by Raman scattering it has been shown that some of the H is bonded to the Si lattice.

Formation and phase transition of VO2 precipitates embedded in sapphire

1999 ◽  
Vol 14 (6) ◽  
pp. 2602-2610 ◽  
Author(s):  
Laurence A. Gea ◽  
J. D. Budai ◽  
L. A. Boatner
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Single Crystals ◽  
Surface Region ◽  
Optical Quality ◽  
Host Lattice ◽  
Near Surface ◽  
Thermally Induced ◽  
Metal Phase Transition

Crystallographically coherent precipitates of vanadium dioxide (VO2) have been formed in the near-surface region of single crystals of sapphire (Al2O3) using a combination of ion implantation and thermal treatments. As in the case of either bulk VO2 single crystals or thin films of VO2, the thermally induced semiconductor-to-metal phase transition of the embedded VO2 precipitates is accompanied by a large hysteretic change in the infrared optical transmission. The VO2 precipitate transition temperature (Tc = 72 to 85 °C) is higher than that of bulk VO2 (Tc = 68 °C) and is sensitive to the implantation conditions. The present results show that the damage resulting from the coimplantation of vanadium and oxygen into an Al2O3 host lattice dictates the final microstructure of the VO2 precipitates and, consequently, affects the transition temperature, as well as the optical quality of the VO2/Al2O3 surface-nanocomposite precipitate system.

scholarly journals New Inferences on the Sun from High-degree Modes: The External Layers and the Equation of State

2001 ◽  
Vol 203 ◽  
pp. 177-179 ◽  
Author(s):  
M. P. Di Mauro ◽  
J. Christensen-Dalsgaard
Keyword(s):  
Equation Of State ◽  
Surface Region ◽  
Helium Abundance ◽  
The Sun ◽  
Near Surface ◽  
Solar Structure ◽  
High Degree

We investigate the structure of the Sun by helioseismic inversion of a set of p-mode frequencies which include new precise observations of modes with high degree obtained from the MDI instrument on the SOHO satellite. Such data have the potential to improve the resolution of the solar structure in the near-surface region, to test the equation of state and constrain the envelope helium abundance.

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