Background gas pressure dependence and spatial variation of spontaneously generated magnetic fields in laser−produced plasmas

1975 ◽  
Vol 46 (4) ◽  
pp. 1493-1498 ◽  
Author(s):  
Roger S. Case ◽  
Fred Schwirzke
Keyword(s):  
Magnetic Fields ◽  
Spatial Variation ◽  
Pressure Dependence ◽  
Gas Pressure ◽  
Background Gas

Effect of Non-equilibrium Pulsed Ejection of Si Species into Background Gas on the Formation of Si Nanocrystallite and Nanocrystal-film

2011 ◽  
Vol 1305 ◽  
Author(s):  
Ikurou Umezu ◽  
Shunto Okubo ◽  
Akira Sugimura
Keyword(s):  
Laser Ablation ◽  
Film Growth ◽  
Pulsed Laser ◽  
Pulsed Laser Ablation ◽  
Hydrogen Gas ◽  
Gas Pressure ◽  
Spatial Confinement ◽  
The Individual ◽  
Background Gas ◽  
Non Equilibrium

ABSTRACTThe Si nanocrystal-films are prepared by pulsed laser ablation of Si target in a mixture of helium and hydrogen gas. The total gas pressure and hydrogen partial gas pressure were varied to control structure of nanocrystal-film. The surface of Si nanocrystallite was hydrogenated and degree of hydrogenation increased with increasing hydrogen partial gas pressure. The aggregate structure of nanocrystal-film depended on both the total gas pressure and the hydrogen partial gas pressure. The former and the latter alter spatial confinement of Si species during deposition and the surface hydrogenation of individual nanocrystal, respectively. Spatial confinement increases probability of collision between nanocrystals in the plume. While, surface hydrogenation prevents coalescence of nanocrystals. The individual or aggregated nanocrystals formed in the plume reach the substrate and the nanocrystal-film is deposited on the substrate. The non-equilibrium growth processes during pulsed laser ablation are essential for the formation of the surface structure and the subsequent nanocrystal-film growth. Our results indicate that the structure of nanocrystal-film depends on the probabilities of collision and coalescence between nanocrystals in the plume. These probabilities can be varied by controlling the total gas pressure and the hydrogen partial gas pressure.

Gas Pressure Dependence of the Heat Transport in Porous Solids with Pores Smaller than 10 μm

2009 ◽  
Vol 30 (4) ◽  
pp. 1329-1342 ◽  
Author(s):  
K. Swimm ◽  
G. Reichenauer ◽  
S. Vidi ◽  
H.-P. Ebert
Keyword(s):  
Heat Transport ◽  
Pressure Dependence ◽  
Gas Pressure ◽  
Porous Solids

Non-equilibrium Growth Processes of Porous TiO2 Nanocrystal-films during Pulsed Laser Ablation

2013 ◽  
Vol 1497 ◽  
Author(s):  
Ikurou Umezu ◽  
Nobuyasu Yagi ◽  
Akira Sugimura ◽  
Takehito Yoshida
Keyword(s):  
Laser Ablation ◽  
Pulsed Laser ◽  
Hierarchical Structures ◽  
Pulsed Laser Ablation ◽  
Rutile Phase ◽  
Gas Pressure ◽  
Target Distance ◽  
Structural Formation ◽  
Background Gas ◽  
Non Equilibrium

ABSTRACTWe performed pulsed laser ablation of titanium dioxide (TiO2) target in O2 background gas. Effects of background gas pressure and substrate target distance on the structure of deposited films are clarified. The hierarchical structures are observed when we change scale of observation. The film deposited on the substrate is composed of primary nanocrystal and secondary porous-aggregated-nanostructures. The primary nanocrystal changes from anatase to rutile phase with increasing background gas pressure or substrate target distance. The porosity of secondary aggregated structure increases with increasing background gas pressure or substrate target distance. The similarity between the effects of background gas and substrate target distance indicates that confinement of the plume between target and substrate is important for structural formation. The non-equilibrium aggregation processes of nanocrystals in the plume and on the substrate are essential for the hierarchical structure of the nanocrystal film.

Gas Pressure Dependence of Photon Emission Accompanying Fracture of Polycrystalline MgO in Nitrogen

2006 ◽  
Vol 317-318 ◽  
pp. 313-316 ◽  
Author(s):  
Tadashi Shiota ◽  
Yasuo Toyoshima ◽  
Kouichi Yasuda ◽  
Yohtaro Matsuo
Keyword(s):  
Pressure Dependence ◽  
Room Temperature ◽  
Photon Emission ◽  
Gas Discharge ◽  
Gas Pressure ◽  
The Other ◽  
Experimental Conditions ◽  
Infrared Photon ◽  
Gas Pressures

The photon emission accompanying fracture of a polycrystalline MgO was investigated at room temperature under N2 gas pressures from 10-4 to 105 Pa. At fracture, the ultraviolet, visible and infrared photon emissions instantaneously increased, and then rapidly decreased in most of the experimental conditions. However, in a N2 gas pressure of around 100 Pa, their peak counts lasted for about 10 milliseconds, and the amount of the UV photon emission was fifteen times larger than those obtained in the other N2 gas pressures. This abrupt increment in the emission was explained by the luminescence due to N2 gas discharge according to the classical Townsend’s theory. In conclusion, the photon emission accompanying fracture of a polycrystalline MgO mainly originated from the excited defects as reported by the authors previously, but the N2 gas discharge had a supplementary effect on the emission around a specific N2 gas pressure.

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