Highly Selective Chemical Vapor Deposition of Tin Diselenide Thin Films onto Patterned Substrates via Single Source Diselenoether Precursors

The distorted octahedral complexes [SnCl4{nBuSe­(CH2)nSenBu}] (n = 2 or 3), (1) and (2), obtained from reaction of SnCl4 with the neutral bidentate ligands and characterized by IR/Raman and multinuclear (1H, 77Se­{1H} and 119Sn) NMR spectroscopy and X-ray crystallography, serve as very effective single source precursors for low pressure chemical vapor deposition (LPCVD) of microcrystalline, single phase tin diselenide films onto SiO2, Si and TiN substrates. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) imaging show hexagonal plate crystallites which grow perpendicular to the substrate surface in the thicker films, but align mostly parallel to the surface when the quantity of reagent is reduced to limit the film thickness. X-ray diffraction (XRD) and Raman spectroscopy on the deposited films are consistent with hexagonal SnSe2 (P3̅m1; a = b = 3.81 Å; c = 6.13 Å), with strong evidence for preferred orientation of the crystallites in thinner (0.5–2 μm) samples, consistent with crystal plate growth parallel to the substrate surface. Hall measurements show the deposited SnSe2 is a n-type semiconductor. The resistivity of the crystalline films is 210 (±10) mΩ cm and carrier density is 5.0 × 1018 cm–3. Very highly selective film growth from these reagents onto photolithographically patterned substrates is observed, with deposition strongly preferred onto the (conducting) TiN surfaces of SiO2/TiN patterned substrates, and onto the SiO2 surfaces of Si/SiO2 patterned substrates. A correlation between the high selectivity and high contact angle of a water droplet on the substrate surfaces is observed.扭曲八面体配合物[SnCl₄{nBuSe(CH₂)ₙSenBu}]（n=2或3，即化合物1和2）由四氯化锡与中性双齿配体反应制得，并经红外/拉曼光谱、多核（¹H、⁷⁷Se{¹H}和¹¹⁹Sn）核磁共振波谱以及X射线晶体学表征，可作为高效单源前驱体，用于在SiO₂、Si和TiN衬底上通过低压化学气相沉积（Low Pressure Chemical Vapor Deposition, LPCVD）制备微晶单相二硒化锡薄膜。扫描电子显微镜（Scanning Electron Microscopy, SEM）与原子力显微镜（Atomic Force Microscopy, AFM）成像结果显示：较厚薄膜中的六方片状晶粒垂直于衬底表面生长；当减少试剂用量以控制薄膜厚度时，晶粒大多平行于衬底表面排列。对沉积薄膜的X射线衍射（X-ray Diffraction, XRD）与拉曼光谱分析结果与六方相SnSe₂（空间群P3̅m1；晶胞参数a = b = 3.81 Å；c = 6.13 Å）相符；在厚度为0.5–2 μm的较薄样品中，晶粒呈现显著的择优取向，这与晶粒平行于衬底表面生长的结果一致。霍尔效应测试表明，所沉积的SnSe₂为n型半导体。该结晶薄膜的电阻率为210(±10) mΩ·cm，载流子浓度为5.0 × 10¹⁸ cm⁻³。实验观察到，使用该类试剂可在光刻图案化衬底上实现高选择性的薄膜生长：沉积过程优先发生在SiO₂/TiN图案化衬底的导电TiN表面，以及Si/SiO₂图案化衬底的SiO₂表面。同时发现，该高选择性与衬底表面上水液滴的高接触角存在相关性。