Urbach rule in photoelectron emission from surface states of low-sized silica

Spectral and temperature dependences of photoelectron emission from surface (interface) states of SiO2 films and nanocompacts in the near UV region were studied. They were interpreted in terms of ‘frozen phonons’ conception and modified three-stage electron emission model. The electron emission analog of optical Urbach rule for low-sized silica was proposed. Optical absorption stage was recognized as the dominant phase of electron emission process. The structure and energy parameters of studied samples were obtained. It was revealed that thin and thick SiO2 films have similar structure parameters while their effective potential barriers differ because of different electron transport conditions. High value of static structural disorder in compacted SiO2 nanopowders is attributed to peculiarities of their ultradispersed structure.