Effect of pH on Optic and Structural Characterization of Chemical Deposited AgI Thin Films

AgI thin films were grown on amorphous commercial glass substrates with chemical bath deposition (CBD) at different pH values (2, 3, 4, 5, 6), 6 hours deposition time and 60 °C. The structure of the nanocrystals was characterized by X-ray diffraction (XRD). The ratio of Ag+ and I- ions changed the crystalline structures. The presence of the Ag+ ions produces the γ-phase of AgI and excess of iodine concentration produces β-phase of AgI. The pH: 4 was like a transition pH for these phases. The number of crystallites per unit area has maximum value at pH: 5, as the structure is re-crystallization to hexagonal phase. Also, the thicknesses of produced thin films were decreased with increased pH values. Therefore, transmission, reflection, extinction coefficients and refractive index of the materials were affected by thicknesses, and calculated to be 32, 35, 3, 11, 9 (%) - 27, 25, 61, 45, 49 (%) - 0.036, 0.032, 0.067, 0.107, 0.075 and 3.21, 3.02, 5.16, 8.35, 5.70 in 550 nm at pH: 2-3-4-5-6 values, respectively. The exciton peaks of AgI were observed at between 320 and 420 nm. Surface properties were investigated by using scanning electron microscopy (SEM).

本数据集采用化学浴沉积（chemical bath deposition, CBD）法，在非晶商用玻璃衬底上制备碘化银（AgI）薄膜，制备参数如下：沉积pH值分别设置为2、3、4、5、6，沉积时长6小时，沉积温度60℃。采用X射线衍射（X-ray diffraction, XRD）对纳米晶的晶体结构进行表征：银离子（Ag+）与碘离子（I-）的比例会改变晶体结构，Ag+的存在会诱导生成AgI的γ相，而碘浓度过量则会生成AgI的β相，pH=4为这两种晶相的转变临界pH值。当pH=5时，单位面积内的微晶数量达到峰值，此时薄膜结构重结晶为六方晶相。此外，所制备薄膜的厚度随pH值升高而降低。因此，薄膜的透射率、反射率、消光系数与折射率均受厚度影响，在550nm波长下，对应pH=2、3、4、5、6的各参数计算结果依次为：透射率32%、35%、3%、11%、9%；反射率27%、25%、61%、45%、49%；消光系数0.036、0.032、0.067、0.107、0.075；折射率3.21、3.02、5.16、8.35、5.70。AgI的激子峰观测波长范围为320~420nm。采用扫描电子显微镜（scanning electron microscopy, SEM）对薄膜的表面性能进行了表征。