A new method of scanning tunneling spectroscopy for study of the energy structure of semiconductors and free electron gas in metals

In this study, a new method for the scanning tun neling spectroscopy (STS) of direct and indirect gap semiconductors and free electron gas in metals is proposed. Band structures of Si, porous Si, and Ge were studied. The tunneling current-voltage characteristics of Si and porous Si surfaces were measured over different voltage intervals from tens of mV to 20 V under incident light from an Xe lamp and those of a Ge surface in the dark. The correlation between the shapes of the I-V curves and band structure of the materials was calculated. It was found that the curves are linear if measured in the voltage range V-o < E-g/(2e) and nonlinear when V-o > E-g/(2e) (in the measurements the applied voltage was changed from - V-o to V-o). The method was used for the observation of a new effect of tunneling of free electron gas having thermal energies from a metal tip to a band gap state of the semiconductor. The energy spectrum of free electron gas was measured.