Electrical properties of low-temperature-grown CaF2 on Si(111)

Abstract

While epitaxial CaF2 films grown on Si(111) at temperatures above 550 °C exhibited flat capacitance-voltage (C-V) curves, suggesting a pinned CaF2/Si(111) interface, we have observed unpinned C-V curves from as-deposited epitaxial CaF2 grown at 300 °C. Our results demonstrate that C-V characteristics of CaF2/Si(111) are determined by the thermal history, rather than the crystalline quality, of the CaF2 film. Correlations among CaF2/Si interface state density, thermal stress, and atomic bonding at the interface are discussed.

Low density of states at the epitaxial - Si(111) interface

“…Considering experimental uncertainties, the density of interface states near midgap is estimated to be well below 3 × 10 12 cm −2 eV −1 . This value is much lower than those reported in the literature for these growth temperatures [5] as well as those estimated in our previous work [6].…”

“…Growth at temperatures around 200-400 • C has been found to result in a low density of interface states in the order of 5 × 10 10 cm −2 , despite the poor crystalline quality of the film, while growth at temperatures above 600 • C leads to higher crystalline quality, but with a completely pinned Fermi level at the interface, i.e. >10 14 cm −2 interface states [5]. These densities of interface states have to compete with values of 10 10 -10 11 cm −2 for the SiO 2 -Si system.…”

Growth characteristics of ultra-thin epitaxial Ca Mg1−F2 alloys on Si(1 1 1) substrates

“…(1 1 1) CaF 2 tunneling barriers for fluoride RTDs are typically as thin as 4-5 ML (1.2-1.5 nm). With respect to crystallinity, the optimum growth temperature for CaF 2 on Si(1 1 1) is around 750 1C [12,13]. However, the lattice mismatch between the CaF 2 layer and the Si substrate at this temperature increases to +1.8% from +0.6% at RT, due to the difference in thermal expansion coefficients between CaF 2 and Si.…”

Observation of Chemical Reactions in Solid Phase Using X-Ray Photoelectron Spectroscopy

“…Si-CaF 2 heterosystem has been quite extensively studied, which is true both for its formation using the MBE method and its electrophysical properties. Existing literature describes results of studying the behaviour of capacitance-voltage C-V characteristics of MISstructures with CaF 2 films grown at different temperatures (Cho et al, 1992). It was shown, that the value of capacity modulation of the obtained structures depends on the temperature of CaF 2 deposition.…”