Band gap of amorphous and well-ordered Al2O3 on Ni3Al(100)

Abstract

The vibrational and electronic properties of amorphous and well-ordered alumina formed on Ni3Al(100) were investigated using high-resolution electron energy loss spectroscopy. The structure of well-ordered alumina was analyzed by low-energy electron diffraction. The amorphous Al2O3 films are prepared by adsorption of O2 at room temperature, while the well-ordered Al2O3 are obtained by direct oxidation of Ni3Al at 1150 K. The band gap energy is ∼3.2 and ∼4.3 eV for amorphous alumina and well-ordered alumina thin films respectively. The lowering of the band gap with respect to the bulk value of Al2O3 is associated with defect-induced states located in the band gap.

Influence of working gas pressure on structure and properties of CuAlO2 films

“…As can be seen, E gd and E gi are around 3.55 and 2.00 eV for CuAlO 2 thin films with difference P W , which are basically consistent with ones of polycrystalline CuAlO 2 thin film (E gd and E gi are around 3.5 and 1.8 eV, respectively) deposited by pulsed laser deposition if taken into account the error induced by the measurement [1,27]. The slight discrepancy might be attributed to the fact that the effect of the different crystallinity on energy gaps [28,29].…”

Unveiling the complex electronic structure of amorphous metal oxides

“…Instead, the peak at 525 eV is not trivial to explain. States just above the VB were previously found by high-resolution electron energy loss spectroscopy in am-Al 2 O 3 and were attributed to coordination imperfection (8). In our calculated electronic spectrum (Fig.…”

“…General features of the electronic structure of amorphous semiconductors are quite well known, such as the broad distribution of coordinations and the lack of long range order that induces valence and conduction band tails in the band gap (6). However, the origin of these states is less explored experimentally (7,8) and theoretical investigations are mainly limited to the crystalline polymorphs (9-11). Amorphous Alumina (am-Al 2 O 3 ) is currently one of the key technological amorphous materials, where one promising application of am-Al 2 O 3 is as a high-k dielectric in transistors (12).…”

Experimental determination of tunneling characteristics and dwell times from temperature dependence of Al/Al2O3/Al junctions

“…Here E g (300 K) ¼ 3.2 eV obtained from Ref. 18 for amorphous Al 2 O 3 and U 0 (300 K) ¼ 1.799 eV from our current data fit. Finally we obtain the temperature dependence of the energy gap from E g (T) ¼ c U 0 (T) in the temperature range between 3.5 and 300 K as given in Fig.…”