Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, 91125, USA.
Bruker Nano Surfaces, 112 Robin Hill Road, Goleta, CA, 93117, USA.
ChemSusChem. 2017 Nov 23;10(22):4657-4663. doi: 10.1002/cssc.201700893. Epub 2017 Aug 7.
The interfacial properties of electrolessly deposited Pt nanoparticles (Pt-NPs) on p-Si and p -Si electrodes were investigated on the nanometer scale using a combination of scanning probe methods. Atomic force microscopy (AFM) showed highly dispersed Pt-NPs with diameters of 20-150 nm on the Si surface. Conductive AFM measurements showed that only approximately half of the particles exhibited measurable contact currents, with a factor of 10 difference in current observed between particles at a given bias. Local current-voltage measurements revealed a rectifying junction with a resistance ≥10 MΩ at the Pt-NP/p-Si interface, whereas the Pt-NP/p -Si samples formed an ohmic junction with a local resistance ≥1 MΩ. The particles were strongly attached to the sample surface in air. However, in an electrolyte, the adhesion of the particles to the surface was substantially lower, and most of the particles had tip-contact currents that varied by a factor of approximately 10. Scanning electrochemical microscopy (SECM) showed smaller but more uniform electrochemical currents for the particles relative to the currents observed by conductive AFM. In accord with the conductive AFM measurements, the SECM measurements showed conductance through the substrate for only a minority of the particles. These results suggest that the electrochemical performance of the electrolessly deposited Pt nanoparticles on Si can be ascribed to: 1) The high resistance of the contact between the particles and the substrate, 2) the low (<50 %) fraction of particles that support high currents, and 3) the low adhesion of the particles to the surface when in contact with the electrolyte.
采用扫描探针方法相结合，在纳米尺度上研究了化学镀 Pt 纳米颗粒（Pt-NPs）在 p-Si 和 p-Si 电极上的界面性质。原子力显微镜（AFM）显示 Si 表面上的 Pt-NPs 具有 20-150nm 的高度分散粒径。导电 AFM 测量表明，只有大约一半的颗粒表现出可测量的接触电流，在给定偏压下，颗粒之间的电流差异高达 10 倍。局部电流-电压测量表明，Pt-NP/p-Si 界面处存在一个具有≥10MΩ电阻的整流结，而 Pt-NP/p-Si 样品则形成一个具有≥1MΩ局部电阻的欧姆结。颗粒在空气中牢固地附着在样品表面上。然而，在电解质中，颗粒与表面的附着力大大降低，大多数颗粒的尖端接触电流变化幅度约为 10 倍。扫描电化学显微镜（SECM）显示，相对于导电 AFM 观察到的电流，颗粒的电化学电流更小但更均匀。与导电 AFM 测量结果一致，SECM 测量结果表明，只有少数颗粒能够通过衬底导电。这些结果表明，化学镀 Pt 纳米颗粒在 Si 上的电化学性能可归因于：1）颗粒与衬底之间接触的高电阻，2）支持高电流的颗粒比例低（<50％），3）当与电解质接触时，颗粒对表面的附着力低。
