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.

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 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.

Induction of high-temperature superconductivity in pulsed laser ablated La2CuO4thin films by room temperature chemical oxidation

1997 ◽  
Vol 9 (10) ◽  
pp. 823-826 ◽  
Author(s):  
Simon T. Lees ◽  
Peter P. Edwards ◽  
Ian Gameson ◽  
Martin O. Jones ◽  
Marcin Slaski ◽  
...  
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
High Temperature Superconductivity ◽  
Pulsed Laser ◽  
Chemical Oxidation

Characterization of pulsed laser deposited Zno-WS2 thin solid film lubricants

1995 ◽  
Vol 53 ◽  
pp. 558-559
Author(s):  
S. D. Walck ◽  
J. S. Zabinski ◽  
N.T. McDevitt ◽  
J. E. Bultman
Keyword(s):  
Thin Films ◽  
High Temperature ◽  
Low Temperatures ◽  
Wear Debris ◽  
Room Temperature ◽  
Pulsed Laser ◽  
Chemical Changes ◽  
Aerospace Applications ◽  
Solid Film

ZnO-WS2 is a potential high temperature solid film lubricant for aerospace applications that exhibits adaptive lubricant behavior. An adaptive lubricant undergoes phase and/or chemical changes in response to thermal, environmental, and tribological conditions; with the resulting phase or wear debris also being lubricious. Pulsed laser deposited (PLD) ZnO-WS2 thin films deposited at room temperature (RT) and wear-tested at room temperature have been shown to have coefficients of friction of 0.04 or less which are comparable to WS2 films, but have much longer wear lives. In the as-deposited state, PLD ZnO-WS2 films are amorphous, but when wear-tested, the phases WS2, WO3, and ZnWO4 are produced. Of these, WS2 is a lubricant phase at low temperatures (⪯ ~450°C) while ZnWO4 is a lubricant phase above about 600°C. The purpose of this work was to characterize the microstructural and chemical changes that occur when the RT-PLD ZnO-WS2 films are heated in air.The RT-PLD ZnO-WS2 films were deposited in a system having a base pressure of 9×l0-7 Pa with a typical pressure during deposition of 6×10-5 Pa.

On the Epitaxy of Metal Films on GaN

1996 ◽  
Vol 449 ◽  
Author(s):  
Q.Z. Liu ◽  
K.V. Smith ◽  
E.T. Yu ◽  
S.S. Lau ◽  
N.R. Perkins ◽  
...  
Keyword(s):  
Room Temperature ◽  
Lattice Mismatch ◽  
Metal Films ◽  
X Ray Diffraction ◽  
X Ray ◽  
Force Microscopy ◽  
Ion Channeling ◽  
Sapphire Substrates ◽  
Atomic Force ◽  
Determining Factor

ABSTRACTA variety of metal films deposited at room temperature have been found to grow epitaxially under conventional vacuum conditions on GaN grown by metalorganic vapor phase epitaxy on sapphire substrates. The metal films have been characterized by X-ray diffraction using a thin-film Read camera and by MeV ion channeling measurements. Lattice mismatch between the epitaxial metals and the GaN basal planes ranges from ∼ 0.2% to ∼ 22%, and does not appear to be the determining factor in the epitaxy reported here. Surface structure of the epitaxial metal films has been studied by atomic force microscopy and found to differ considerably from that of nonepitaxial metal films grown on similar GaN substrates.

Microstructures and Mechanical Properties of Co3(Al,W) with the L12 Structure

2008 ◽  
Vol 1128 ◽  
Author(s):  
Takashi Oohashi ◽  
Norihiko L. Okamoto ◽  
Kyosuke Kishida ◽  
Katsushi Tanaka ◽  
Haruyuki Inui
Keyword(s):  
Mechanical Properties ◽  
Thermal Expansion ◽  
High Temperature ◽  
Physical Properties ◽  
Room Temperature ◽  
Single Phase ◽  
Lattice Mismatch ◽  
Solid Solution Phase ◽  
High Temperature Strength ◽  
L12 Structure

AbstractSince the ternary intermetallic compound Co3(Al,W) with the L12 structure was discovered, two-phase Co-base alloys composed of the γ-Co solid-solution phase and the γ'-Co3(Al,W) phase as a strengthening phase have been investigated as promising high-temperature materials. Some Co-base alloys have been reported to exhibit high-temperature strength greater than those of conventional Ni-base superalloys. Although the excellent high-temperature physical properties of the Co-based alloys are considered to result from the phase stability and strength of Co3(Al,W), the pristine physical properties of Co3(Al,W) have not been fully understood, supposedly due to the difficulties in obtaining single-phase Co3(Al,W). In the present study, we examine the effect of heat treatment on the microstructure of alloys with compositions close to single-phase Co3(Al,W) as well as their mechanical properties, e.g. elastic modulus, thermal expansion, etc., in hope of deriving the pristine properties of the Co3(Al,W) phase. A single crystal with the composition of Co-10Al-11W grown by floating-zone melting exhibits a thermal expansion coefficient of 10×10-6 K-1 at room temperature, which is virtually identical to those of the commercial Ni-base superalloys. However, it increases with increasing temperature followed by a discontinuity at around 1000°C, inferring the phase transformation from γ' to γ. The investigated thermal expansion behavior indicates that the lattice mismatch between the γ' and γ phases is reversed from positive at room temperature to negative at high temperatures above around 500°C. The results of elastic property measurement and environmental embrittlement investigation of polycrystalline Co3(Al,W) will also be presented.

Epitaxial growth of antiperovskite GaCMn3 film on perovskite LaAlO3 substrate

2002 ◽  
Vol 17 (10) ◽  
pp. 2640-2643 ◽  
Author(s):  
H. S. Choi ◽  
W. S. Kim ◽  
J. C. Kim ◽  
N. H. Hur
Keyword(s):  
Transport Properties ◽  
Epitaxial Growth ◽  
Room Temperature ◽  
Lattice Mismatch ◽  
Compressive Strain ◽  
Pulsed Laser ◽  
Bulk Sample ◽  
Laser Deposition ◽  
Strain Effect ◽  
Deposition Technique

We report on the magnetic and transport properties of the antiperovskite GaCMn3 film epitaxially grown on LaAlO3 using the pulsed laser deposition technique. Upon cooling from room temperature, the GaCMn3 film undergoes magnetic transitions from paramagnetic to ferromagnetic to antiferromagnetic. The Curie and Neél temperatures of the film shift to lower and higher temperatures, respectively, by comparison with those of the bulk sample. This discrepancy is mainly ascribed to the compressive strain effect induced by the lattice-mismatch between film and substrate. Negative magnetoresistance, which is about 20% at 0.5 T, is observed near the Neél temperature.

TEM sample preparation of wear-tested room-temperature pulsed-laser-deposited thin films of MoS2 by ultramicrotomy

1993 ◽  
Vol 51 ◽  
pp. 1118-1119
Author(s):  
Pamela F. Lloyd ◽  
Scott D. Walck
Keyword(s):  
Thin Films ◽  
Sample Preparation ◽  
Room Temperature ◽  
High Vacuum ◽  
Pulsed Laser ◽  
Ultra High Vacuum ◽  
Wear Testing ◽  
Preparation Technique ◽  
Cross Sectional ◽  
Aerospace Applications

Pulsed laser deposition (PLD) is a novel technique for the deposition of tribological thin films. MoS2 is the archetypical solid lubricant material for aerospace applications. It provides a low coefficient of friction from cryogenic temperatures to about 350°C and can be used in ultra high vacuum environments. The TEM is ideally suited for studying the microstructural and tribo-chemical changes that occur during wear. The normal cross sectional TEM sample preparation method does not work well because the material’s lubricity causes the sandwich to separate. Walck et al. deposited MoS2 through a mesh mask which gave suitable results for as-deposited films, but the discontinuous nature of the film is unsuitable for wear-testing. To investigate wear-tested, room temperature (RT) PLD MoS2 films, the sample preparation technique of Heuer and Howitt was adapted.Two 300 run thick films were deposited on single crystal NaCl substrates. One was wear-tested on a ball-on-disk tribometer using a 30 gm load at 150 rpm for one minute, and subsequently coated with a heavy layer of evaporated gold.

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