The enhanced optical property of chemical passivated n type GaSb
In the paper, Te-doped n type GaSb was passivated by (NH4)2S, the optical and surface properties of passivated GaSb were investigated by PL and AFM. After passivation treatment, the luminescence intensity of GaSb was enhanced. The passivation time would also affect luminescence intensity and the surface smooth of GaSb.
Structure and stability of passivating arsenic sulfide phases on GaAs surfaces
Passivating AsxSy phases that form on GaAs after reactions with aqueous sulfides [Na2S⋅9H2O and (NH4)2S] decompose in the presence of oxygen and light, producing a surface composed primarily of As2O3. X‐ray photoelectron spectroscopy (XPS) shows that (NH4)2 S‐treated surfaces degrade in two steps with the initial AsxSy (present as a disulfide) degrading by S–S bond cleavage to yield As2O3 and an As2S3 phase like the one that forms on GaAs after Na2S⋅9H2O reactions. XPS reveals little decomposition of surface sulfides in the presence of light or oxygen alone, showing that GaAs passivation could be made long‐lived if either is rigorously excluded.
Intensification of Bubble Disintegration and Dispersion by Mechanical Stirring in Gas Injection Refining
Water model experiments were performed for establishing highly efficient gas injection refining processes. Mechanical stirring was applied to disintegrate the injected bubbles and to disperse them widely in the bath. The bubble disintegration and dispersion were investigated by changing rotation mode (direction of rotation), rotation speed, blade size of the impeller and gas flow rate. Forward rotation of the impeller induced a stable tangential flow and could not disperse bubbles in the bath due to formation of a vortex around the impeller shaft. The tangential flow could be suppressed by forward–interrupt rotation, which could reduce the vortex formation to some degree. However, forward–interrupt rotation could not disperse the bubbles widely in the bath. Forward–reverse rotation could prevent the vortex formation completely and create a strong shear stress field, which intensified the bubble disintegration and dispersion in the bath. Higher impeller rotation speed and larger blade length in forward–reverse rotation could enhance the bubble disintegration and make the dispersed bubbles smaller. The bubble dispersion zone became wider with larger blade length. The bubble size tended to be larger at higher gas flow rates. However, its dependence on the gas flow rate became smaller at higher impeller rotation speed.