Investigation of Electronic and Structural Properties of Tin Compounds under Extreme Pressure*

Many heavy metal oxides have been predicted to have unique electronic properties. One such material is SnO2, which is a wide band-gap semiconductor. SnO2 has been shown to have the unique property of its band gap opening with pressure. Utilizing a combination of X-ray diffraction, X-ray absorption, Raman, and UV absorption, we have attempted to probe this unique phenomenon. By combining these techniques with ground state structure predictions, along with Reverse Monte Carlo fitting to determine local order from EXAFS, we have begun to understand the structural and electronic configurations of SnO2. One difficulty with these measurements and analysis is that SnO2 is known to have kinetically hindered phase transitions. By utilizing in situ CO2 laser annealing at each pressure point, we have been able to access the true ground state structures that have been predicted from theoretical structure searching.