Trap creation in ultrathin SiO2 films due to electron injection studied by scanning tunneling microscopy/scanning tunneling spectroscopy

✦ Synopsis

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. Ž . Scanning tunneling microscopy STM and scanning tunneling spectroscopy STS have been employed for the investigation of trap creation in ultrathin SiO films on an atomic scale. Bright spots created by electron injection using 2 STM tips were observed in STM images. The density of bright spots depends on the injection voltage and temperature. Comparing STS spectra obtained from electron-injected SiO films with those from a fresh film, we have found that the 2 bright spots are related to positively charged traps in the SiO films and caused a band bending near the SirSiO interface.

Oxygen interaction of CdS-based gas sens

Oxygen interaction of CdS-based gas sensors with different stoichiometric compositions was studied by X-ray photoelectron spectroscopy (XPS) and thermal-desorption mass spectroscopy observations combined with conductivity measurements. Three different types of film with different atomic ratios of Cd/S were used in the study of oxygen chemisorption in a low-temperature range between 300 and 570 K. Spray pyrolysis was used for the deposition of the films on glass substrates; XPS and energy dispersive spectroscopy of X-ray together with atomic force microscopy and scanning electron microscopy were used for the characterization of the composition and structure of the films. It was possible to distinguish different temperature ranges for the thermal desorption of the different adsorbed oxygen species. A comparison of the data from XPS and mass-spectroscopy observations with conductance measurements allows to conclude that metallic surface atoms are responsible for different interactions of oxygen species with CdS surfaces.

📂 Article 📅 1995 🏛 Elsevier Science 🌐 English ⚖ 379 KB