Ionization behavior of deep level donors in passive film formed on surface of stainless steel in 5% salt solution

Deep level donor＇s ionization behavior of passive film formed on the surface of stainless steel was investigated by Mott-Schottky plots. It is indicated that transformation process of deep level donors＇ ionization behavior of passive film on surface of stainless steel can be divided into 4 stages with rising immersion time. At the initial immersion stage （10 min）, Fe（II） located in the octahedral sites of the unit cell is not ionized and the deep level does not appear in Mott-Schottky plots. At the second stage （9-38 h）, Fe（II） located in the octahedral sites starts to be ionized, which results in deep level donors＇ generation and density of deep level donors almost is constant with augmenting immersion time but the thickness of space charge layer is more and more thicker with rising immersion time. At the third stage （48 h-12 d）, density of deep level donors rises with increasing immersion time and the thickness of passive films space charge layer decreases. At last stage （above 23 d）, both the space charge layer＇s thickness and density of deep level donors are no longer changed with increasing immersion time. In the overall immersion stage, the shallow level donors＇ density is invariable all the time. The mechanism of deep level donor＇s ionization can be the generation of metal vacancies, which results in crystal lattice＇s aberration and the aberration energy urges the ionization of Fe（ II ） in octahedral sites.

Constructing interfacial electric field and Zn vacancy modulated ohmic junctions ZnS/NiS for photocatalytic H_(2) evolution

Adjusting the interfacial transport efficiency of photogenerated electrons and the free energy of hydrogen adsorption through interface engineering is an effective means of improving the photocatalytic activity of semiconductor photocatalysts.Herein,hollow ZnS/NiS nanocages with ohmic contacts containing Zn vacancy(V_(Zn)-ZnS/NiS)are synthesized using ZIF-8 as templates.An internal electric field is constructed by Fermi level flattening to form ohmic contacts,which increase donor density and accelerate electron transport at the V_(Zn)-ZnS/NiS interface.The experimental and DFT results show that the tight interface and V_(Zn) can rearrange electrons,resulting in a higher charge density at the interface,and optimizing the Gibbs free energy of hydrogen adsorption.The optimal hydrogen production activity of V_(Zn)-ZnS/NiS is 10,636 mmol h^(-1) g^(-1),which is 31.9 times that of V_(Zn)-ZnS.This study provides an idea for constructing sulfide heterojunctions with ohmic contacts and defects to achieve efficient photocatalytic hydrogen production.

Semiconducting behavior of the anodically passive films formed on AZ31B alloy

This work includes determination of the semiconductor character and estimation of the dopant levels in the passive film formed on AZ31B alloy in 0.01 M NaOH,as well as the estimation of the passive film thickness as a function of the film formation potential.Mott-Schottky analysis revealed that the passive films displayed n-type semiconductive characteristics,where the oxygen vacancies and interstitials preponderated.Based on the Mott-Schottky analysis,it was shown that the calculated donor density increases linearly with increasing the formation potential.Also,the electrochemical impedance spectroscopy(EIS)results indicated that the thickness of the passive film was decreased linearly with increasing the formation potential.The results showed that decreasing the formation potential offer better conditions for forming the passive films with higher protection behavior,due to the growth of a much thicker and less defective films.

Optimization of Mo/Cu(In,Ga)Se2/CdS/ZnO Hetero-Junction Solar Cell Performance by Numerical Simulation with SCAPS-1D

The paper presents a one-dimensional simulation study of chalcopyrite Cu(In,Ga)Se2(CIGS)solar cells,where the effects of the variation of CIGS,CdS,and ZnO layers are presented.Additionlly the influence of the variation of doping and the defects density of shallow uniform donors and acceptors types are also presented.The analyse of the simulation results shows that recombination inside the space charge region(SCR)decrease more our CIGS solar cell model performance.We also found that the electrical parameters increase with increasing CIGS absorber doping density exception of JSC values that reach their maximum at 1016cm-3 and decrease due to recombination of charge carriers in the p-n junction particularly the recombination inside the SCR.We also stressed the fact that the effects of shallow uniforme donor density is very low on the performance of our CIGS solar cell model is important because it will allow to control the width of space charge region from shallow uniform acceptors defect density that has a strong influence on the different electrical parameters.Yet,good optimization of performance of the CIGS-based solar cell necessarily passes though a good control of the space charge region width and will constitute a boosting perspective for the preparation of our next paper.We contact that the results obtained of the numerical simulation with SCAPS-1D show a good agreement comparatively of the literature results.The simulation of our CIGS solar cell presents best performances if the values of the absorber layer thickness is in the range of 0.02 to 0.03μm,the buffer layer thickness is in the range of 0.02 to 0.06μm and the defects density of shallow uniform acceptors types is in the range of 1015 to 1017cm-3.