Donor and Acceptor Levels in Undoped β-FeSi₂ Films Grown on Si (001) Substrates

Abstract

We sought evidence of the dopant segregation phenomenon and the formation of a dopant-segregation-induced insulating layer in Nb-doped BaTiO 3 , by impedance and modulus analyses. In a 0.05 mol% Nb-doped specimen in which dopant segregation is not expected to occur, impedance and modulus data over the range of 30-400 • C can be explained by the conventional positive-temperature-coefficient-resistor (PTCR) equivalent circuit of grain resistance (R) and grain boundary resistance and capacitance (C). In a 0.4 mol% Nb-doped specimen, however, impedance and modulus data can be described by introducing another third RC component in addition to the grain and grain boundary component. This RC component is assumed to have originated from the dopant segregation layer. Above 350 • C, this RC component associated with segregation layer begins to disappear. This phenomenon can be explained by the Fermi level change and the valence change of the titanium vacancy in the dopant segregation layer with change in temperature.

Electrical Properties of β-FeSi2 Thin Films on Insulating Substrates

“…From the slope of σ above 600K in Figs. Takakura et al [11]. This value is an approximately equal to the value of 0.42±0.05eV, which was reported for the single crystal by G. Behr et al [10].…”

Effect of Cu or Co addition on β-FeSi2 growth by molten salt method

“…It is considered that the p-type conduction is due to (1) the low Si/Fe content [23][24][25], (2) the formation of a domain boundary [5], and (3) the unintentionally doped impurity [26]. The acceptors are compensated by the Co doping, moreover, the ntype conduction appears at greater than a 1.5 mol% Co addition.…”

Indirect optical absorption and origin of the emission from β-FeSi2 nanoparticles: Bound exciton (0.809 eV) and band to acceptor impurity (0.795 eV) transitions

“…40,41 Thus, the 0.795 eV transition corresponds to a recombination of an electron in the conduction band to a hole in the deep acceptor level, with binding energy of 72 meV on top of the valence band. Therefore, the 0.795 eV corresponds to a direct transition, being the direct fundamental gap given by E g direct = 0.795 eV + 0.072 eV = 0.867 eV, ͑5͒…”