Tunable large field magnetoconductance of ZnO, ZnMnO, and ZnCoO thin films

Abstract

Magnetoconductivity of ten ZnO, Zn1−xCoxO, and Zn1−xMnxO thin films with nominal concentrations of 2.0 at.% and 0.1 at.% of Co2+ and Mn2+ ions, respectively, has been analyzed in the temperature range from 5 K to 200 K in in-plane and out-of-plane magnetic fields up to 6 T. The formation of a highly conducting surface layer can be controlled during thin film deposition, leading to a large variation of the sheet resistance, namely, from 2 × 103 Ω/◻ to 1 × 105 Ω/◻ at room temperature. Depending on the thickness of the highly conducting surface layer, a single two-dimensional (2D), a single three-dimensional (3D), or a two-dimensional and three-dimensional (2D + 3D) parallel conducting model was chosen to analyze the measured magnetoconductivity of the magnetic ZnO thin films with different electron spins (S=5/2 for Zn1−xMnxO and S=3/2 for Zn1−xCoxO) and with different Landé g-factors (isotropic for 3D Zn1−xMnxO and 2D Zn1−xCoxO and anisotropic for 2D Zn1−xMnxO and 3D Zn1−xCoxO).

Increased static dielectric constant in ZnMnO and ZnCoO thin films with bound magnetic polarons

“…The resistance of the ZnO has been measured and the transport properties are classified 28,29 by ranges of resistance in Table 1. Insulating ZnO thin films have lower ε r while low conducting ZnO and moderate conducting ZnO thin films have higher ε r which is an indication of the dielectric constant dependence on donor concentration.…”

“…We investigated the species of shallow donors in ZnO thin films grown by pulsed laser deposition by assuming two different donors with two thermal activation energies in the ZnO. For example, in our previous work Vegesna et al 28 the existence of two different donors could (E a 1 = 1.54 meV and E a 2 = 82.75 meV) be proven by modeling the temperature dependent free carrier concentration. This thermal activation energy hints towards hydrogen related defects and zinc interstitials.…”

Analysis of Low-Temperature Magnetotransport Properties of NbN Thin Films Grown by Atomic Layer Deposition

“…F σ significantly increased with a decrease in temperature to T c (Figure 5). For magnetic oxide semiconductor thin films we observed that F σ decreased with a decrease in temperature [7]; however, for superconducting thin films we saw an increase in F σ with a decrease in temperature towards T c . This could be interpreted in terms of a strong repulsive force experienced by the electrons around the Fermi energy when approaching T c .…”

“…In our earlier work [6,7], we measured and analysed the transport properties of semiconductor thin films (3D) and of semiconductor ultrathin films (2D) in an external in-plane and out-of-plane magnetic field. The resistance of the investigated semiconductors, e.g., magnetic conducting oxides, increased when the temperature decreased.…”