Institute of Electronics, Silesian University of Technology, Gliwice 44-100, Poland.
CNR- SPIN & Department of Physics and Chemical Sciences University of L'Aquila, L'Aquila 67100, Italy.
Nanoscale Res Lett. 2014 May 24;9(1):260. doi: 10.1186/1556-276X-9-260. eCollection 2014.
This is well known that the selectivity and sensitivity of tin dioxide (SnO2) thin film sensors for the detection of low concentration of volatile sulfides such as H2S in air can be improved by small amount of Ag additives. In this paper we present the results of comparative X-ray photoelectron spectroscopy (XPS), thermal desorption spectroscopy (TDS), and atomic force microscopy (AFM) studies of the surface chemistry and morphology of SnO2 nanolayers obtained by laser-enhanced chemical vapor deposition (L-CVD) additionally covered with 1 monolayer (ML) of Ag. For as deposited SnO2 nanolayers, a mixture of tin oxide (SnO) and tin dioxide (SnO2) with the [C]/[Sn] ratio of approximately 1.3 was observed. After dry air exposure, the [O]/[Sn] ratio slightly increased to approximately 1.55. Moreover, an evident increasing of C contamination was observed with [C]/[Sn] ratio of approximately 3.5. After TDS experiment, the [O]/[Sn] ratio goes back to 1.3, whereas C contamination evidently decreases (by factor of 3). Simultaneously, the Ag concentration after air exposure and TDS experiment subsequently decreased (finally by factor of approximately 2), which was caused by the diffusion of Ag atoms into the subsurface layers related to the grain-type surface morphology of Ag-covered L-CVD SnO2 nanolayers, as confirmed by XPS ion depth profiling studies. The variation of surface chemistry of the Ag-covered L-CVD SnO2 after air exposure observed by XPS was in a good correlation with the desorption of residual gases from these nanolayers observed in TDS experiments.
众所周知，通过添加少量的银（Ag）添加剂，可以提高二氧化锡（SnO2）薄膜传感器对空气中低浓度挥发性硫化物（如 H2S）的选择性和灵敏度。本文介绍了通过激光增强化学气相沉积（L-CVD）制备的 SnO2 纳米层表面化学和形貌的 X 射线光电子能谱（XPS）、热脱附光谱（TDS）和原子力显微镜（AFM）研究结果，这些纳米层额外覆盖了 1 个单层（ML）的 Ag。对于沉积的 SnO2 纳米层，观察到氧化锡（SnO）和二氧化锡（SnO2）的混合物，[C]/[Sn] 比约为 1.3。在干燥空气暴露后，[O]/[Sn] 比略微增加到约 1.55。此外，观察到 C 污染明显增加，[C]/[Sn] 比约为 3.5。在 TDS 实验后，[O]/[Sn] 比回到 1.3，而 C 污染明显减少（减少了 3 倍）。同时，空气暴露和 TDS 实验后的 Ag 浓度随后降低（最终降低了约 2 倍），这是由于 Ag 原子扩散到与 Ag 覆盖的 L-CVD SnO2 纳米层的晶粒型表面形貌相关的次表层，这一点通过 XPS 离子深度剖析研究得到了证实。XPS 观察到的空气暴露后 Ag 覆盖的 L-CVD SnO2 表面化学变化与 TDS 实验中观察到的这些纳米层中残留气体的解吸很好地相关。
