Electrical and emission properties of nanocomposite SiOx(Si) and SiO2(Si) films

Abstract

The electrical and emission properties of as deposited and annealed SiOx(Si) films have been investigated. The films with thicknesses of 10–100nm were obtained by thermal evaporation of silicon powder in vacuum (2.7–4.0)×10−3Pa on flat Si substrates and Si tip arrays. The atomic force microscopy investigations of the surface morphology indicated the presence of nanoprotrusions on surface of the initial SiOx(Si) films with height up to 20nm and curvature radius of the nanoprotrusions about 3–5nm. As a result of the thermal annealing, the film surface becomes more uniform and its morphology is characterized by nanoprotrusions with height in the range of 1–3nm. At low electric fields the I-V characteristics of dark current through the initial SiOx(Si) films correspond to Poole-Frenkel transport mechanism. The Fowler-Nordheim tunneling dominates at higher electric fields. As to annealed SiO2(Si) films, the modified Fowler-Nordheim electron tunneling through trapezoidal SiO2 barrier between silicon nanoclusters restricts the current flow. The effective electron field emission from Si tip arrays coated with nanocomposite SiOx(Si) and SiO2(Si) films was observed. The results of the electron field emission from surface of SiOx(Si) films into vacuum show an emission current density of 0.25×10−5A∕cm2 at macroscopic electric fields of (5–6)×105V∕cm. The field emission from thermally annealed samples was not observed in the whole range of the applied voltages. In the contrary, for the case of thermally annealed samples subjected to the following partial etching in HF:H2O solution, the emission increases in comparison with initial samples. In this case the field emission appears already at an electric field of 1.5×105V∕cm and the maximum current density increases up to the value of ∼3×10−5A∕cm2. The current peaks are revealed on emission I(V) characteristics built in J(E) coordinates. The models for explanation of peculiarities of the electrical conductivity and electron field emission from nanocomposite films are discussed.