Ultrahigh vacuum surface analysis studies of electrochemical atomic layer deposition of metals and compound semiconductors
Kim, Jay Yu
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The main topic of this dissertation is electrochemical atomic layer deposition (ALD) by ultrahigh vacuum (UHV) surface analysis. The purpose of electrochemical ALD is to form smooth thin films at room temperature. The first part of this dissertation will be about platinum (Pt) and copper (Cu) electrochemical ALD on gold (Au) substrate. The surface-limited redox replacements (SLRR) were used in these cases. In case of forming a Pt atomic layer, a Cu atomic layer, as a sacrificial layer, was first formed by underpotential deposition (UPD) on the clean and annealed Au(111) single crystal. Then, it was immersed in the Pt solution at open circuit, and a Cu atomic layer was replaced spontaneously by Pt ions, so a Pt atomic layer was formed on the substrate. To form multiple Pt atomic layers, the subsequent Pt replacements with Cu sacrificial layers were done on the substrate. In order to grow Cu atomic layers on the substrate, lead (Pb) ííatomic layers were used as the sacrificial layers. I and Cl anions were used in solutions for electrochemical annealing. Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and scanning tunneling microscopy (STM) were performed to estimate the quality of the thin films on the substrate. The second part of this dissertation is about the electrochemical ALD on GaAs(100) substrate. After the substrate was cleaned, an attempt was made to deposit a Te atomic layer on the substrate. A Te atomic layer on the substrate is expected as a precursor to deposit metals, such as cadmium (Cd) or indium (In). From the Auger ratios of In/Te and Te/Ga, the In2Te3 atomic layer was attempted to form on the substrate. The deposited In2Te3 thin film thickness was calculated from the Auger electron spectra. The future plan with this GaAs(100) substrate is to form atomic layers of InSb, Sb2Te3, and In2Sb2Te3.