Photocurrent Response In Mg-Doped GaN

1997 ◽  
Vol 482 ◽  
Author(s):  
C. H. Qiu ◽  
J. I Pankove ◽  
I. Akasaki ◽  
H. Amano
Keyword(s):  
Thin Films ◽  
Time Domain ◽  
Low Temperatures ◽  
Room Temperature ◽  
Photocurrent Response ◽  
Defect States ◽  
Maximum Value ◽  
The Time Domain ◽  
Photoconductivity Response ◽  
Mg Doped

AbstractThe photoconductivity response of Mg-doped GaN thin films was studied in the time domain of 50 nanoseconds to a few milliseconds in the temperature range of 100K to 390K. The response time, defined as the time when the photocurrent decreased to half its maximum value, is in the sub-microseconds at room temperature, but increased to a few microseconds at low temperatures. The contact capacitance is suspected for this behavior. Slower decay components due to trapping at defect states were also observed.

Transport Properties of Granular Nix(SiO2)100−x Thin Films

1990 ◽  
Vol 195 ◽  
Author(s):  
John R. Beamish ◽  
B.M. Patterson ◽  
K.M. Unruh
Keyword(s):  
Thin Films ◽  
Temperature Dependence ◽  
Electrical Transport ◽  
Low Temperatures ◽  
Room Temperature ◽  
Volume Percent ◽  
Ni Content ◽  
Resistivity Minimum ◽  
Temperature Coefficient Of Resistivity ◽  
Sputter Deposited

ABSTRACTWe have studied the electrical transport behavior of sputter deposited Nix(SiO2)100−x thin films between room temperature and 100 mK and, at selected temperatures, in applied magnetic fields up to 6 T. As the Ni concentration x is reduced, the resistivity increases systematically. At a Ni concentration (nominal) of about x–70 atomic percent (38 volume percent) the room temperature coefficient of resistivity changes sign. For Ni concentrations greater than 70 percent the resistance first decreases with temperature then increases logarithmically at, low temperatures. This increase becomes smaller and the resistivity minimum moves to progressively lower temperatures as the Ni concentration increases. In films with less than x–70 percent Ni, the resistivity has a temperature dependence of the form ρ(T)–ρo exp \(To/T)α] between room temperature and about 5 K. The exponent a is about 1/2 and To increases with decreasing Ni content. Below 1 K, however, the resistivity increases much less rapidly, with a temperature dependence independent of Ni concentration. In all films the magnetoresistance is small and negative.

scholarly journals Experimental Study on the Spanwise Correlation of Vortex-Induced Force Using Large-Scale Section Model

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Chunguang Li ◽  
Yu Mao ◽  
Yan Han ◽  
Kai Li ◽  
C.S. Cai
Keyword(s):  
Time Domain ◽  
Large Scale ◽  
Correlation Coefficients ◽  
Box Girder ◽  
Pressure Coefficients ◽  
Smooth Flow ◽  
Maximum Value ◽  
Section Model ◽  
The Time Domain ◽  
Lock In

To investigate the spanwise correlation of vortex-induced forces (VIF) of a typical section of a streamlined box girder, wind tunnel tests of simultaneous measurement of force and displacement responses of a sectional model were conducted in a smooth flow. The spanwise correlation of VIF and pressure coefficients on the measurement points of an oscillating main deck were analyzed in both the time domain and frequency domain, respectively. The research results indicated that the spanwise correlation of VIF and pressure coefficients on the measurement points were related to the amplitudes of vortex-induced vibration (VIV), both of them weakened with the increase of spanwise distance; the maximum value of spanwise correlation coefficient is situated at the ascending stage of the lock-in region, rather than at the extreme amplitude point. The amplitudes of VIV showed different impacts on the spanwise correlation of pressure coefficients on the measurement points of the upper and lower surfaces, for which the maximum value of the spanwise correlation coefficients is located at the extreme amplitude point and the ascending stage of the lock-in region, respectively. Furthermore, the spanwise correlation of the pressure coefficients decreases continually from the upstream to downstream of the main deck; large coherence of vortex-induced forces and pressure appears around the frequency of vortex shedding, and the coherence of VIF and pressure becomes smaller with the increase in the spanwise distance.

Study of magnetic and transport properties of Bi2Se3/FeSe2 bilayer thin films

2021 ◽  
Vol 35 (02) ◽  
pp. 2150022
Author(s):  
J. Zhang ◽  
K. Zhao ◽  
X. S. Yang ◽  
Y. Zhao
Keyword(s):  
Thin Films ◽  
Proximity Effect ◽  
Low Temperatures ◽  
Smooth Surface ◽  
Room Temperature ◽  
Magnetic Order ◽  
Spin Orbit Coupling ◽  
Bilayer Films ◽  
Linear Magnetoresistance ◽  
Strong Spin

Thin films of topological insulator (TI) Bi2Se3 were grown onto the surfaces of FeSe2 layers of different thicknesses on Si (100) substrates by magnetron sputtering, forming bilayer films with smooth surface. Magnetic and transport measurements indicate ferromagnetism in these bilayer samples. Large coercive fields at low-temperatures and a room-temperature magnetic order were observed. Moreover, nonsaturated high-filed linear magnetoresistance (MR) and weak anti-localization effect were found in these bilayer thin films. These results indicate that the bilayer samples could have both strong spin–orbit coupling and ferromagnetic proximity effect, which are the desired features.

The Effect of Annealing on the Cu Distribution and AI2Cu Precipitation in Ai(Cu) Thin Films

1993 ◽  
Vol 309 ◽  
Author(s):  
E.G. Colgan ◽  
K.P. Rodbell ◽  
D.R. Vigliotti
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Grain Boundaries ◽  
Low Temperatures ◽  
Room Temperature ◽  
Annealing Temperature ◽  
Precipitate Morphology ◽  
Electromigration Lifetime ◽  
Bamboo Structure ◽  
Anneal Temperature

AbstractThe Cu distribution in AI(Cu) thin films has been examined in blanket and patterned samples as a function of annealing. The Cu concentration in the Al grains, measured at room temperature, closely follows the solubility at the anneal temperature when a high cooling rate is used (-100 or -200°C/min) from the annealing temperature. With fine lines, the room temperature Cu concentration follows the solubility at the anneal temperature only at low anneal temperatures, ≤350°C. With higher temperatureannealing, >400°C, the room temperature Cu concentration in the Al grains was substantially less than the solubility at the anneal temperature. These differences are attributed to the smaller grain size in fine lines, which reduces the distance to grain boundaries. With blanket films, the Θ-phase (Al2Cu) precipitate morphology depends on the Al grain size and annealing temperature. With small Al grains (100-300 nm), the Θ particles are small (100-200 nm) and round whereas with large Al grains (0.5-2μm), the precipitates are long and irregularly shaped. The morphology of the Θ precipitates is constrained by the Al grain size. With fine lines, having a bamboo structure, the Θ precipitates are “wedge” shaped along grain boundaries or span the width of the line. The electromigration lifetime was found to depend strongly on the heat treatment used, an increase of 3X in lifetime was obtained for samples rapidly cooled from a temperature above the solvus curve as compared with samples subjected to additional aging at low temperatures. This is believed to be dueto the different concentrations of Cu in solution and to the size and distribution of Θparticles in the patterned lines.

Substantiation of a Technique of Determining Stress in Thin Films at Very Low Temperatures

2015 ◽  
Vol 14 ◽  
pp. 28-36
Author(s):  
C.C. Chama
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Low Temperatures ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
High Temperature Stress ◽  
Hysteresis Curves ◽  
Stress Hysteresis

Substantiation of a technique earlier employed in determining stress in Copper-Silver thin films at very low temperatures is presented. It is shown that the stress measured at elevated temperatures using Stoney’s equation can be utilized in the determination of stress at very low temperatures. To demonstrate the application of this technique, a case study has been conducted by utilizing stress hysteresis curves obtained from the Cu-6at%Ag thin film heated from room temperature to 400°C and cooled back to room temperature in two cycles. The stresses in the Cu-6at%Ag thin film at various low temperatures up to-197°C have been determined by utilizing data from high temperature stress hysteresis curves.

In-Plane Thermal and Thermoelectric Properties of Polycrystalline Highly Preferred Orientation [(W)x(WSE2)y]z Superlattice Thin Films

2007 ◽  
Author(s):  
Anastassios Mavrokefalos ◽  
Ngoc T. Nguyen ◽  
Michael T. Pettes ◽  
David C. Johnson ◽  
Li Shi
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Thermoelectric Properties ◽  
Time Domain ◽  
Preferred Orientation ◽  
Laser Reflectance ◽  
Thermoelectric Energy ◽  
Measurement Results ◽  
The Time Domain

It was recently found by using the time domain thermal reflectance method that polycrystalline highly preferred orientation WSe2 and [(W)x(WSe2)y]z superlattice films possess extremely low cross-plane thermal conductivity, which is desirable for thermal insulation and thermoelectric energy conversion applications. However, it is difficult to obtain the in-plane thermal conductivity by using the laser reflectance or the 3-ω method. Here we employ a suspended microdevice developed for measuring thermoelectric properties of individual nanowires and nanofilms to obtain the in-plane thermal conductivity, electrical conductivity, and Seebeck coefficient of [(W)x(WSe2)y]z superlattice films. The measurement results show that the in-plane thermal conductivities of these films are much higher than the cross-plane values, making the thermal conductivity of the films highly anisotropic.

scholarly journals Synthesis Thin Films SnO2 with Doping Indium by Sol-gel Spin coating

2019 ◽  
Vol 5 (2) ◽  
pp. 171 ◽  
Author(s):  
Syamsul Hakim ◽  
Aris Doyan ◽  
Susilawati Susilawati ◽  
Lalu Muliyadi
Keyword(s):  
Thin Films ◽  
Experimental Study ◽  
Spin Coating ◽  
Low Temperatures ◽  
Room Temperature ◽  
Sol Gel ◽  
Temperature Variations

Abstract:This research is an experimental study that aims to support the temperature and variation of doping in making thin films. The temperature variations at room temperature annealing, 50, 100, 150, and 200oC, and doping variations of 0, 5, 10, 15, 20, and 25%. The method used in this study is sol-gel spin coating. The results showed that thin films at low temperatures were more transparent than higher temperatures and the increase percentage doping causing thin films to be more transparent. Keywords:Thin Films; SnO2; Indium, Sol-gel, Spin Coating.

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.

Low-Temperature Growth of Thin Films of A12O3 with Trimethylaluminum and Hydrogen Peroxide

1991 ◽  
Vol 222 ◽  
Author(s):  
J. F. Fan ◽  
K. Sugioka ◽  
K. Toyoda
Keyword(s):  
Thin Films ◽  
Hydrogen Peroxide ◽  
Low Temperature ◽  
Chemical Reaction ◽  
Low Temperatures ◽  
Arbitrary Shape ◽  
Room Temperature ◽  
Surface Chemical ◽  
Surface Chemical Reaction ◽  
Temperature Growth

ABSTRACTThin films of A12O3 were prepared by sequential surface chemical reaction of trimethylaluminum and hydrogen peroxide at low temperatures. It has been found that hydrogen peroxide reacts very easily with trimethylaluminum, resulting in growth of A12O3 at the temperature as low as the room temperature. Another favorable feature of the technique is that the growth of excellent A12O3 occurs identically wherever the reactants reach, making it possible to completely coat the surface of the sample with arbitrary shape.

Temperature Dependence of the Electrical Conductivity of Poly(Benzo[1,2-b:4,5-b'] Dithiophene-4,8-Diyl Vinylene) and Poly(Dodecylthiophene)

1997 ◽  
Vol 488 ◽  
Author(s):  
R. C Hyer ◽  
R. G. Pethe ◽  
T. Yogi ◽  
S. C. Sharma ◽  
J. Wang ◽  
...  
Keyword(s):  
Thin Films ◽  
Electrical Conductivity ◽  
Temperature Dependence ◽  
Low Temperatures ◽  
Room Temperature ◽  
Thermal Fluctuation ◽  
Variable Range Hopping ◽  
Tunneling Model ◽  
Three Samples ◽  
Electrical Conductivities

AbstractWe present results for the electrical conductivity (σ) of thin films of poly(benzo[1,2-b:4,5- b']dithiophene-4,8-diyl vinylene) (PBDV) and poly (dodecylthiophene) (PDDT) as a function of temperature in the range 15-295K. The polymers were doped with FeC13 and PF6 which resulted in electrical conductivities differing by two orders of magnitude at room temperature. We examine three sets of σ(T)-data by using the variable-range hopping (VRH) model that predicts a linear relationship between ln(T1/2σ) and T1/4. We observe a change in the slope of the ln(T1/2σ) vs T14 relationship in all three samples at low temperatures. We also analyze the temperature dependence of the resistivity of PBDV by using the thermal fluctuation-induced tunneling model.

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