Laser-Induced Multi-Crystallization of Thin Germanium Films

1988 ◽  
Vol 129 ◽  
Author(s):  
C. Ortiz ◽  
K.A. Rubin ◽  
S. A. Iuria
Keyword(s):  
Pulse Length ◽  
Laser Pulses ◽  
Beam Diameter ◽  
Amorphous Films ◽  
Small Spot ◽  
Laser Beam Irradiation ◽  
Crystalline Films ◽  
Kinetics Of ◽  
Deposited Films ◽  
Laser Pulse Length

ABSTRACTWe report here the crystallization kinetics of thin (35nm and 60nm) amorphous as-deposited Ge filins using diffraction limited laser beam irradiation and laser pulses between 30ns and IreS. The recrystallization of crystalline as-deposited films was also studied for similar laser conditions. Crystallization was observed for pulses as short as 50ns. We conclude that the use of small beam spots (-1μm) gives a very different crystallization morphology from that observed previously for larger beam diameter and same laser pulse length. In our case for short irradiation times, the nucleation process dominates over crystal growth. Laser irradiation of as-deposited crystalline films produced grains with significantly less defects than grains crystallized from as-deposited amorphous films. Temperature calculations allow us to understand these results by showing that only the small spot irradiation sustains the material at high temperature for times comparable to the pulse width.

Laser-induced multicrystallization events of thin germanium films

1988 ◽  
Vol 3 (6) ◽  
pp. 1196-1200 ◽  
Author(s):  
C. Ortiz ◽  
K. A. Rubin ◽  
S. Ajuria
Keyword(s):  
Pulse Length ◽  
Laser Pulses ◽  
Beam Diameter ◽  
Amorphous Thin Films ◽  
Small Spot ◽  
Laser Beam Irradiation ◽  
Crystalline Films ◽  
Kinetics Of ◽  
Deposited Films ◽  
Laser Pulse Length

The crystallization kinetics of thin (35 and 60 nm) amorphous as-deposited Ge films were studied using diffraction limited laser beam irradiation and laser pulses between 30 ns and 1 ms. The recrystallization of crystalline as-deposited films was also studied for similar laser conditions. Crystallization was observed for pulses as short as 50 ns. It was concluded that the irradiation of amorphous thin films with small beam spots (∼ 1μm) gives a very different crystallization morphology from that observed previously for larger beam diameter and same laser pulse length. In the present case for short irradiation times, the nucleation process dominates over crystal growth. Temperature calculations allow the understanding of these results by showing that only the small spot irradiation sustains the material at high temperature for times comparable to the pulse width. Laser irradiation of as-deposited crystalline films produced grains with significantly fewer defects than grains crystallized from as-deposited amorphous films.

scholarly journals Wakefield effects on the evolution of symmetric laser pulses in a plasma channel

2010 ◽  
Vol 28 (2) ◽  
pp. 245-251 ◽  
Author(s):  
Pallavi Jha ◽  
Amita Malviya ◽  
Ajay K. Upadhyay
Keyword(s):  
Laser Pulse ◽  
Evolution Equations ◽  
Plasma Channel ◽  
Pulse Length ◽  
Laser Pulses ◽  
Spot Size ◽  
Propagation Characteristics ◽  
Short Laser Pulses ◽  
Parabolic Plasma ◽  
Laser Pulse Length

AbstractThe present study deals with the propagation of short laser pulses in a parabolic plasma channel. A variational technique is used to obtain simultaneous evolution equations describing the laser pulse length and spot size in the presence of relativistic and ponderomotive nonlinearities. The effect of wakefields (inside the pulse) on the propagation characteristics of the laser beam is studied. Numerical methods are used to graphically analyze the evolution of the laser pulse length and intensity.

High Purity Titanium Silicide Films Formed by Sputter Deposition and Rapid Thermal Annealing

1987 ◽  
Vol 92 ◽  
Author(s):  
T. Brat ◽  
J.C.S. Wei ◽  
J. Poole ◽  
D. Hodul ◽  
N. Parikh ◽  
...  
Keyword(s):  
Tensile Stress ◽  
High Purity ◽  
Room Temperature ◽  
Titanium Silicide ◽  
Amorphous Films ◽  
Si Substrates ◽  
Crystalline Films ◽  
Order Of Magnitude ◽  
Sputter Deposited ◽  
Deposited Films

ABSTRACTWe have investigated the formation of titanium silicide films sputter deposited from a high purity (99.995%) composite TiSi2.2 target. The films, sputtered at a rate of 3.7 nm/sec, were deposited on Si(100), Si02 , and N+ Poly-Si substrates at temperatures ranging from room temperature to 425°C. Room temperature depositions produced amorphous films, while heated substrate depositions formed crystalline films with a metastable C49 TiSi2 structure. Rapid thermal processing of these films at temperatures higher than 700°C resulted in the formation of a stable C54 TiSi2 structure. Stoichiometry of the deposited films over a 10 cm diameter wafer was found to be independent of the substrate temperature. Stress in the films was measured as a function of deposition and annealing parameters. The amorphous films showed a tensile stress of about 0.1 GPa, while films deposited on substrates at 425°C had an order of magnitude higher tensile stress level.The resistivity measured on the 400°C deposited films was about half of that obtained with the films deposited at roomtemperature. A comparison between films deposited on a hot substrate and those which were rapid thermal processed is presented.

Ultrafast Laser Cleaning of Daguerreotypes

2011 ◽  
Vol 1319 ◽  
Author(s):  
Michael J. Abere ◽  
Ryan D. Murphy ◽  
Bianca Jackson ◽  
Gerard Mourou ◽  
Michel Menu ◽  
...  
Keyword(s):  
Material Removal ◽  
Silver Oxide ◽  
Laser Pulses ◽  
Silver Sulfide ◽  
Ultrafast Laser ◽  
Beam Diameter ◽  
Chemical Cleaning ◽  
Silver Substrate ◽  
Fs Laser ◽  
Lower Material

ABSTRACTAn ultrafast laser irradiation method for the removal of corrosion from Daguerreotypes without detrimentally affecting image quality has been developed. Corrosion products such as silver oxide and silver sulfide may be removed by chemical cleaning but these reactions are hard to control and are often damaging to the underlying silver, ruining the image. The Ti:Sapphire 150 fs laser pulses used in this study are focused to a beam diameter of 60 μm and are normally incident to the Daguerreotype. It was found that the corrosion layer has a lower material removal threshold than silver allowing for removal of corrosion with minimal removal of vital information contained in the silver substrate.

Langevin approach to plasma kinetics with Coulomb collisions

1999 ◽  
Vol 61 (1) ◽  
pp. 89-106 ◽  
Author(s):  
M. G. CADJAN ◽  
M. F. IVANOV
Keyword(s):  
Laser Pulses ◽  
Intense Laser ◽  
Plasma Parameters ◽  
Plasma Dynamics ◽  
Coulomb Collisions ◽  
Numerical Tests ◽  
Langevin Approach ◽  
Intense Laser Radiation ◽  
Overdense Plasma ◽  
Kinetics Of

The Langevin approach to the kinetics of a collisional plasma is developed. Some collision models are considered, and the corresponding stochastic differential equations are derived. These equations can be regarded as an alternative to the description of a plasma in terms of a distribution function. The method developed here allows one to simulate plasma processes, taking account of both collective kinetics effects and Coulomb collisions. Results of the numerical simulation of the intervention of laser pulses with an overdense plasma are presented. The dependence of the absorption coefficient on the plasma parameters is calculated. The features of the plasma dynamics under the action of intense laser radiation are observed and discussed. The results of numerical tests of the validity of this method are also presented.

EFFECTS OF Al, Ga-DOPING ON TRANSPARENT CONDUCTING PROPERTIES OF AMORPHOUS ZnO-SnO2 FILMS

2006 ◽  
Vol 20 (25n27) ◽  
pp. 3902-3907 ◽  
Author(s):  
TOSHIHIRO MORIGA ◽  
YUSUKE NISHIMURA ◽  
HIROSHI SUKETA ◽  
KEI-ICHIRO MURAI ◽  
KAZUHIRO NOGAMI ◽  
...  
Keyword(s):  
Visible Region ◽  
Doping Effect ◽  
Amorphous Films ◽  
Current Ratio ◽  
Transparent Films ◽  
Glass Substrates ◽  
Transparent Conducting ◽  
Region 10 ◽  
Ga Doping ◽  
Deposited Films

ZnO SnO 2 thin films were deposited on glass substrates (Corning#1737) by DC magnetron sputtering. In this works, we examined a doping effect on a ZnO target on transparent conducting properties. ZnO:Al (4wt%), and ZnO:Ga (6wt%) targets were used for a dopant-free ZnO target. Substrate temperature was held at 250°C. The current ratio δ was defined as IZn/IZ + ISn ( ZnO target current divided by the sum of ZnO and SnO 2 target currents). Compositions of as-deposited films were changed with the current ratio δ. In the ZnO-SnO 2 system, amorphous transparent films appeared over the range of 0.33≤δ≤0.73. On the other hand, in the ZnO:Al (4 wt %)- SnO 2 and ZnO:Ga (6 wt %)- SnO 2 systems, they appeared over the range of 0.20≤δ≤0.80 and 0.33≤δ≤0.80, ≤δ≤ respectively. The minimum resistivity of amorphous films was about 3.0×10-2 Ω cm for all the systems. Al , Ga doping effect on film resistivity was not clear very much. But optical transparencies were 80-90% in visible region, 10% higher than those of ZnO-SnO 2 system at average. Optical band gap for the films with the same current ratio δ also was enhanced by the Al , Ga doping.

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