Surface properties of semiconductor crystals play a significant role in the operation of different devices like transistors, LEDs, and solar cells. For better performance of the devices, it is essential to minimize the amount of harmful surface and interface defects. For example, control over the oxygen induced defects is difficult during deposition of any film (e.g., metal oxide films) on a semiconductor crystal. On the other hand, tailoring and characterization of the semiconductor interfaces is not an easy task due to the buried nature of these structures. 

In this thesis, we have studied the effect of different adsorbates (Sr, Ba, Si, and Sb) and metal oxides (BaO, SiO2, Al2O3 and Sb2O3) on different semiconductor surfaces: Si(100), Ge(100) and GaAs(100). In this experimental work, several complementary characterization methods were used including low energy electron diffraction (LEED), synchrotron-radiation photoemission spectroscopy (SR- PES) and scanning tunneling microscopy (STM). These results were interconnected to capacitance-voltage (CV) and photoluminescence (PL) measurements via collaboration with other research groups. 

The results can be summarized as follows: It is demonstrated the reduction in the defects amount at Al2O3/GaAs interface when an intermediate thin layer of BaO was deposited before atomic layer deposition of Al2O3. In the case of epitaxial BaO/SiO2 system, the crystallinity of the interface even after the incorporation of significant amount of oxygen atoms into Si is an interesting finding. It is also evident in this research that metal interaction with semiconductor substrate can also induce degradation in the interface. This degradation can be avoided with the modification of starting surface and by adopting a specific procedure for oxide film growth. Furthermore, a growth of crystalline Sb2O3 film has been also presented by careful consideration of deposition temperature and time.