Spectral transmittance and module structure fitting for transmission-mode GaAs photocathodes
Spectral transmittance and module structure fitting for transmission-mode GaAs photocathodes
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DOI：
10.1088/1674-1056/20/4/047801
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发表时间：
2011-04
影响因子：
1.7
通讯作者：
赵静;常本康;熊雅娟;张益军
中科院分区：
文献类型：
--
作者：
赵静;常本康;熊雅娟;张益军
透射式GaAs光电阴极包括四层玻璃、Si 3 N4、Ga 1 −xAlxAs和GaAs。采用分子束外延技术制备了梯度掺杂的光电阴极样品，用分光光度计测量了样品在600 ~ 1100 nm范围内的透过率。基于薄膜光学的矩阵公式，推导了薄膜的理论透过率，并进行了数值模拟。模拟结果表明，过渡层和除玻璃外的三层薄膜对透射谱的影响。此外，误差修正所需的拟合系数进入拟合公式。拟合结果表明，修正后的公式在全谱范围内的相对误差由19.51%降低到4.35%。得到了相对误差最小时对应的系数和膜厚，模块中各层膜厚和总膜厚偏差均控制在7%以内。玻璃层的粗糙度，层界面效应和表面氧化物的存在解释的修改。
A transmission-mode GaAs photocathode includes four layers of glass, Si3N4, Ga1−xAlxAs and GaAs. A gradient-doping photocathode sample was obtained by molecular beam epitaxy and its transmittance was measured by spectrophotometer from 600 nm to 1100 nm. The theoretical transmittance is derived and simulated based on the matrix formula for thin film optics. The simulation results indicate the influence of the transition layers and the three thin-film layers except glass on the transmittance spectra. In addition, a fitting coefficient needed for error modification enters into the fitted formula. The fitting results show that the relative error in the full spectrum reduces from 19.51% to 4.35% after the formula is modified. The coefficient and the thicknesses are gained corresponding to the minimum relative error, meanwhile each layer and total thin-film thickness deviation in the module can be controlled within 7%. The presence of glass layer roughness, layer interface effects and surface oxides is interpreted on the modification.