The influence of Sn doping on the growth of In2O3 on Y-stabilized ZrO2(100) by oxygen plasma assisted molecular beam epitaxy

Abstract

The influence of Sn doping on the growth of In 2 O 3 on Y-stabilized ZrO 2 ͑100͒ by oxygen plasma assisted molecular beam epitaxy has been investigated over a range of substrate temperatures between 650 and 900°C. The extent of dopant incorporation under a constant Sn flux decreases monotonically with increasing substrate temperature, although the n-type carrier concentration in "overdoped" films grown at 650°C is lower than in films with a lower Sn concentration grown at 750°C. The small increase in lattice parameter associated with Sn doping leads to improved matching with the substrate and suppresses breakup of the films into square islands observed in high temperature growth of undoped In 2 O 3 on Y-stabilized ZrO 2 ͑100͒. Plasmon energies derived from infrared reflection spectra of Sn-doped films are found to be close to satellite energies in core level photoemission spectroscopy, but for a nominally undoped reference sample there is evidence for carrier accumulation at the surface. This influences both the In 3d core line shape and the intensity of a peak close to the Fermi energy associated with photoemission from the conduction band.

Dopant and Defect Induced Electronic States at In2O3 Surfaces

“…However, it is likely that Sn doping also changes the balance of surface energies. A systematic study of the temperature dependence of the influence of Sn doping is complicated by the fact that the extent of Sn accommodation into a growing film under a constant Sn flux decreases strongly with increasing substrate temperature [163]. This was tentatively attributed to the fact that Sn forms a volatile lower oxide SnO, in contrast to In where the corresponding N-2 oxide (where N refers to the group oxidation state) In 2 O is not known.…”

“…Sn-doping has been observed to exert a large influence on the morphology of In 2 O 3 films grown on YSZ(001) by MBE [25,149,154,163]: in general incorporation of Sn leads to flatter and less fragmented surfaces and suppresses the propensity for island formation. This appears to be due in part to the fact that Sn doping leads to an increase in the lattice parameter of In 2 O 3 , thus lowering the mismatch with the substrate.…”

“…This was tentatively attributed to the fact that Sn forms a volatile lower oxide SnO, in contrast to In where the corresponding N-2 oxide (where N refers to the group oxidation state) In 2 O is not known. The quality of Sn doped In 2 O 3 (001) surfaces is sufficiently good to allow observation of well-defined LEED patterns with the expected 4-fold symmetry [25,163] and achievement of atomically resolved STM images [25].…”

“…A consequence of this is that the definition of conduction band states relative to the background coming from valence band states actually improves with increasing photon energy, provided that data are acquired for long enough. Thus Al Kα XPS [14,28,105,158,163] and more recently hard XPS [30,58,178] have become the techniques of choice for photoemission studies of conduction electrons in TCOs.…”

Synthesis and electronic properties of Ruddlesden-Popper strontium iridate epitaxial thin films stabilized by control of growth kinetics

“…ther the emergence of two different final states, i.e. screened and un-screened core holes 44,45 or the existence of plasmon satellites in the higher binding energy range 46,47 . According to the Kotani model 48 , for narrow band metals the core hole generated in the photoemission process interacts with conduction carriers and thereby creates two different (screened and unscreened) final sates.…”