Amorphous Gallium Produced By Pulsed Excimer Laser Irradiation

1985 ◽  
Vol 51 ◽  
Author(s):  
J. Fröhlingsdorf ◽  
B. Stritzker
Keyword(s):  
Transition Temperature ◽  
Energy Density ◽  
Excimer Laser ◽  
Low Temperatures ◽  
Threshold Energy ◽  
Residual Resistivity ◽  
Superconducting Transition ◽  
Β Phase ◽  
Excimer Laser Irradiation ◽  
Vapor Quenching

ABSTRACTPure crystalline Ga films (α-Ga, β-Ga) have been irradiated at low temperatures (≤ 20 K) with an Excimer laser. By measuring the superconducting transition temperature Tc and the residual resistivity ≤o, the resulting Ga phases (α-Ga, β-Ga, a-Ga) can be identified.Both crystalline Ga phases can be transformed into the amorphous phase.The threshold energy density for the β→ a transition depends on the film thickness, whereas the α →. a transition occurs always at about 225 mJ/cm2 This behavior is in agreement with earlier observations that a-Ga can grow on top of the in-phase but not on the β-phase.The results of laser quenching are compared with other non-equilibrium techniques for the production of a-Ga, such as vapor quenching and low temperature ion iradiation.

Electron Irradiation of YBa2Cu3O7 at low Temperatures

1987 ◽  
Vol 99 ◽  
Author(s):  
B. Stritzker ◽  
W. Zander ◽  
F. Dworschak ◽  
U. Poppe ◽  
K. Fischer
Keyword(s):  
Transition Temperature ◽  
Electron Irradiation ◽  
Normal State ◽  
Low Temperatures ◽  
Superconducting Transition Temperature ◽  
Superconducting Transition ◽  
Radiation Induced ◽  
State Resistance ◽  
Normal State Resistance

ABSTRACTBulk samples of YBa2Cu3O7−x have been homogenously irradiated with 3 MeV electrons at temperatures below 20 K. Whereas the superconducting transition temperature, Tc, drops dramatically with increasing dose the width of the transition remains unchanged (Δ Tc ≤ 1.5 K). The normal state resistance at 100 K increases substantially during the electron irradiation. Several irreproducible experiments can be interpreted with a radiation induced, unstable increase of Tc.

Excimer Laser Crystallization of Nanocrystalline Silicon Thin Films

2015 ◽  
Vol 1120-1121 ◽  
pp. 361-368
Author(s):  
Li Jie Deng ◽  
Wei He ◽  
Zheng Ping Li
Keyword(s):  
Thin Films ◽  
Energy Density ◽  
Excimer Laser ◽  
Silicon Film ◽  
Threshold Energy ◽  
Nanocrystalline Silicon ◽  
Lateral Growth ◽  
Laser Crystallization ◽  
Silicon Thin Films ◽  
Excimer Laser Crystallization

Nanocrystalline silicon (nc-Si) thin film on glass substrate is subjected to excimer laser crystallized by varying the laser energy density in the range of 50~600 mJ/cm2. The effect of excimer laser crystallization on the structure of silicon film is investigated using Raman spectroscopy, X-ray diffraction, atomic force microscopy and scanning electron microscopy. The results show that polycrystalline silicon thin films can be obtained by excimer laser crystallization of nc-Si films. A laser threshold energy density of 200 mJ/cm2 is estimated from the change of crystalline fraction and surface roughness of the treated films. The growth of grain is observed and the crystallization mechanism is discussed based on the super lateral growth model. The nanocrystalline silicon grains in the films act as seeds for lateral growth to large grains.

Laser Irradiation of Ge(100): An Assessment of Surface Order with He Diffraction

1984 ◽  
Vol 35 ◽  
Author(s):  
W. R. Lambert ◽  
P. L. Trevor ◽  
M. T. Schulberg ◽  
M. J. Cardillo ◽  
J. C. Tully
Keyword(s):  
Laser Irradiation ◽  
Excimer Laser ◽  
Low Temperatures ◽  
Thermal Response ◽  
Surface Damage ◽  
Experimental Results ◽  
Excimer Laser Irradiation ◽  
Effects Of Irradiation On ◽  
He Atom

ABSTRACTWe investigate the effects of Nd:YAG and excimer laser irradiation on the Ge(100) surface under UHV conditions over a temperature range 140 < T(K) < 300 using the surface sensitive probe of He atom diffraction. We study the effects of irradiation on surface damage and order using the apparent (2×1) ࢐ c(2×4) transition. We monitor surface contamination in situ. The temporal thermal response is modeled theoretically to aid in assessing the experimental results. The capability to maintain a Ge(100) surface at low temperatures free of contamination and well ordered is demonstrated.

Plasma Dynamics During Pulsed Laser Evaporation of High Tc Superconductors

1990 ◽  
Vol 201 ◽  
Author(s):  
Rajiv K. Singh ◽  
R. Neifeld ◽  
J. Narayan
Keyword(s):  
Theoretical Model ◽  
Energy Density ◽  
Excimer Laser ◽  
Pulsed Laser ◽  
Laser Wavelength ◽  
Laser Evaporation ◽  
Degree Of Ionization ◽  
Plasma Dynamics ◽  
Excimer Laser Irradiation

AbstractWe have theoretically and experimentally investigated the dynamics of the evaporated material generated by nanosecond excimer laser irradiation of YBa2Cu3O7 targets in vacuum. The velocity distribution and the ionization of the plasma were determined by the ion time of flight measurements. The excimer laser ablated species possessed very high velocities (> 106 cm/sec) which increased non-linearly with energy density. The ionization/ volume of the evaporated material exhibited a weak dependence on energy density, thereby suggesting the role of nonthermal mechanisms in the ionization process. These experimental results have been correlated with the theoretical model analyzing the plasma dynamics during pulsed laser evaporation of materials. A new modification to the earlier theoretical model is developed which accurately predicts the terminal velocities and the effect of ionization on these velocities. Various factors including, evaporation rates, degree of ionization, and laser wavelength which affect the plasma velocities will also be discussed.

TRANSPORT PROPERTIES OF La2-x1Srx1CuO4+δ/La2-x2Srx2CuO4+δ MULTILAYERS GROWN BY LASER ABLATION

2013 ◽  
Vol 27 (15) ◽  
pp. 1362029
Author(s):  
H. F. WANG ◽  
Y. Z. ZHANG ◽  
L. H. LIU ◽  
D. P. LI ◽  
G. Y. WANG ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Laser Ablation ◽  
Transport Properties ◽  
Low Temperatures ◽  
Superconducting Transition Temperature ◽  
Dominant Factor ◽  
Deposition Condition ◽  
Superconducting Transition ◽  
Charge Redistribution ◽  
Transport Measurements

A series of La 2-x1 Sr x1 CuO 4+δ/ La 2-x2 Sr x2 CuO 4+δ multilayers were epitaxially grown on (001) LaSrAlO 4 and (001) SrTiO 3 substrates by laser ablation, where x1 = 0.0, 0.08 (underdoped) and x2 = 0.24, 0.32, 0.45 (over-doped). Before the depositions of each multilayer, all of the single layers were deposited and characterized, and then the multilayers were deposited by using the same deposition condition except shifting targets for laser ablation. These multilayers are highly c-axis oriented. Several modulation wavelengths of the sublayers were selected for preparing the multilayers. The resistance measurements of these single layered films of La 2-x1 Sr x1 CuO 4+δ, La 2-x2 Sr x2 CuO 4+δ, and multilayers of La 2-x1 Sr x1 CuO 4+δ/ La 2-x2 Sr x2 CuO 4+δ were performed and compared. The transport measurements suggest that the charge redistribution may be a dominant factor for the superconducting transition temperature in low temperatures.

DOPING AND TEMPERATURE DEPENDENCE OF SUPERFLUID DENSITY IN KINETIC ENERGY DRIVEN CUPRATE SUPERCONDUCTORS

2010 ◽  
Vol 24 (29) ◽  
pp. 2845-2854
Author(s):  
ZHEYU HUANG ◽  
HUAISONG ZHAO ◽  
SHIPING FENG
Keyword(s):  
Transition Temperature ◽  
Kinetic Energy ◽  
Temperature Dependence ◽  
Low Temperatures ◽  
Cuprate Superconductors ◽  
Superfluid Density ◽  
Linear Temperature Dependence ◽  
Superconducting Transition ◽  
Zero Temperature ◽  
Linear Temperature

Within the kinetic energy driven superconducting mechanism, the doping and temperature dependence of the superfluid density in cuprate superconductors is studied throughout the superconducting dome. It is shown that the superfluid density shows a crossover from the linear temperature dependence at low temperatures to a nonlinear one in the extremely low temperatures. In analogy to the dome-like shape of the doping dependent superconducting transition temperature, the maximal zero-temperature superfluid density occurs around the critical doping δ ≈ 0.195, and then decreases in both lower doped and higher doped regimes.

Orientation Dependence of Flux Pinning in a Layered Bi2Sr2 Ca1 Cu2O8 + 10% Ag Composite

1991 ◽  
Vol 235 ◽  
Author(s):  
Maria Foldeaki ◽  
Hassel Ledbetter
Keyword(s):  
Transition Temperature ◽  
Low Temperatures ◽  
Grain Orientation ◽  
Orientation Dependence ◽  
Zero Field ◽  
Pinning Force ◽  
Superconducting Transition ◽  
Two Phase ◽  
Random Direction ◽  
Strong Pinning

ABSTRACTThe Bi2 Sr2 Ca1 Cu2 O8 + 10% Ag specimen was grain oriented along the a(b) axis, but random in the perpendicular plane. Magnetic susceptibility and hysteresis measured along the axis of grain orientation and in the polycrystalline direction showed remarkable anisotropy. At low temperatures (below about 30 K), hysteresis curves were compatible with the strong-pinning model. The pinning force calculated from the hysteresis loop showed a higher maximum in the random direction, but decreased fast with increasing field and temperature. From the zero-field-cooled (zfc) and field-cooled (fc) susceptibility curves, the irreversibility line T*(H*) was determined. Evaluation according to the de Almeida-Thouless equation with fixed exponent n=3/2 revealed a two-phase vortex structure; one nearly isotropic with low (40-$K) zero-field irreversibility transition temperature, and one strongly anisotropic, the irreversibility transition being close to the superconducting-transition temperature.

Excimer Laser Induced Cryoetching of GaAs and Related Materials

1992 ◽  
Vol 279 ◽  
Author(s):  
Michael B. Freiler ◽  
Ming Chang Shih ◽  
R. Scarmozzino ◽  
R. M. Osgood ◽  
Ie Wei Tao ◽  
...  
Keyword(s):  
Electron Beam ◽  
Excimer Laser ◽  
Electron Beam Lithography ◽  
Low Temperatures ◽  
Structural Damage ◽  
Ridge Waveguide ◽  
Single Quantum ◽  
Single Quantum Well ◽  
Excimer Laser Irradiation ◽  
193 Nm

ABSTRACTWe report highly resolved, damage-free etching of GaAs and related materials. The etching is activated by excimer laser irradiation at 193 nm of samples maintained at low temperatures (∼140 K) in a chlorine atmosphere (∼5 mTorr). Since the etching is chemical in nature, structural damage to the substrate should not be present. Submicrometer resolution has been achieved by the use of electron beam lithography to pattern a Si3N4 contact mask. We have also successfully used our etching in the fabrication of a single-quantum-well, ridge-waveguide semiconductor laser.

Copper ohmic contacts to n-type SiC formed with pulsed excimer laser irradiation

2001 ◽  
Vol 680 ◽  
Author(s):  
K. Abe ◽  
M. Sumitomo ◽  
O. Eryu ◽  
K. Nakashima
Keyword(s):  
Energy Density ◽  
Laser Irradiation ◽  
Excimer Laser ◽  
Ohmic Contacts ◽  
Laser Energy ◽  
Contact Layer ◽  
Ohmic Behavior ◽  
Current Voltage ◽  
Excimer Laser Irradiation ◽  
Current Voltage Characteristics

ABSTRACTCopper-based ohmic contacts to n-type 6H-SiC have been investigated. In this study, ohmic contacts have been fabricated with pulsed excimer laser irradiation to Cu-deposited substrates at room temperature. It is shown that current-voltage characteristics depend on the laser energy density. Contacts formed by the laser irradiation at the energy density above 1.2 J/cm2 have shown the ohmic behavior. Cu atoms have slightly diffused into SiC by the laser irradiation at 1.4 J/cm2. As a result, a thin ohmic contact layer has been obtained by the laser processing. AES and XRD study have revealed that a Cu-SiC alloy containing Cu silicide (Cu3Si) is formed by the laser irradiation.

Sign in / Sign up

Export Citation Format

Share Document