OPTICAL PROPERTIES OF Cr/Si(001) INTERFACES

摘要

In modern microelectronics Me/Si interfaces are widely used. Such structures can be used as functional materials in microelectronics and as catalysts for oxidation of the silicon surface. The influence of chromium on the change of the optical characteristics of Cr/Si(001) interfaces at their oxidation is investigated. Optical conductivity of interfaces associated with interband transitions in the interval from 1 to 4.5 eV is calculated on the basis of experimentally measured values of ellipsometric parameters $ho$ and $Delta$. This feature of the optical conductivity spectrum is characteristic for the CrSi$_2$ compound. It should be noted that the optical properties of the Cr/Si(001) interface are strongly dependent on the thickness of chromium film, but only when its thickness is less than 2 nm. When the thickness of the chromium film is more than 20 nm, the optical conductivity spectra are affected only by the electronic transitions in the chromium film. The experimental results show that the thin chromium film deposited on the silicon surface facilitates the process of oxidation of the silicon. The most active catalyst is the film with the thickness of 0.5 monolayer. It was discovered that oxidation significantly affects the optical conductivity of Cr films with the thickness less than 2nm. At the same time, the optical spectra of the film with the thickness of 2 nm indicates the presence of a large number of uncompensated surface states. Thus, this structure is promising for the manufacturing of the chemical sensors. The results of this study can be used also for the creation of new microelectronics components and enhancement of oxidation of the silicon surface. However, oxidation process of these structures requires further research to identify optimal thickness of the catalyst film.