Copper Oxidation Studied by In Situ Raman Spectroscopy

摘要

The growing importance of copper in the semiconductor industry has led to a renewed interest in the properties and growth modes of copper oxides under a variety of conditions. While thermal oxidation of copper has been studied extensively over the last decades, recent surface studies seem to ignore the possible formation of Cu_3O_2. It has been shown earlier that thermal oxidation of copper leads to multilayer structures, which consist of Cu_xO, Cu_2O, Cu_3O_2 and CuO, depending on the oxidation conditions. These oxides were analysed ex situ using X-ray Photoelectron Spectroscopy (XPS) combined with depth profiling, Linear Sweep Voltammetry (LSV) and Galvanostatic Reduction (GR). In this work it will be shown that Raman Spectroscopy can be used to follow the formation of the different copper oxides in situ. The experiments were performed using a Raman Microscope with a sample heating extension, which enables in situ copper oxidation in air between room temperature and 300 °C. Raman spectra were acquired in the range between 3000 Δcm~(-1) to 150 Δcm~(-1). From these spectra one can see that Cu2O is formed between 70 °C and 130 °C, Cu_3O_2 is formed between 150 °C and 250 °C and CuO starts to form at temperatures higher than 250 °C.