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Oxide semiconductors are attractive materials for thin-film electronics and optoelectronics due to compatibility with synthesis on large-area, inexpensive glass and flexible plastic substrate. However, development of thin-film electronics has been hampered by the limited number of semiconducting oxides that are p-type. Here, we report on the properties of zinc-cobalt-oxide (Zn–Co–O) films, deposited at room temperature using pulsed laser deposition, that exhibit p-type conduction. Films are deposited at room temperature in a background of oxygen using a polycrystalline ZnCo2O4 ablation target. The p-type conduction is confirmed by positive Seebeck coefficient and positive Hall coefficient. Both electrical resistivity and carrier density are dependent on oxygen background pressure used during deposition. Zn–Co–O films deposited in 50 mTorr oxygen pressure appear to be amorphous based on x-ray diffraction, and show an electrical conductivity as high as 21 S cm-1. Distinct rectifying current-voltage characteristics are observed for junctions between Zn–Co–O and n-type InGaZnO films, exhibiting a threshold voltage of ∼2.5 V. P-type Zn–Co–O appears promising for thin-film electronic device technology. [ABSTRACT FROM AUTHOR]

The magnetic and transport properties of Mn-doped ZnO thin films co-doped with P are examined. Superconducting quantum interference device magnetometry measurements indicate that the films are ferromagnetic with an inverse correlation between magnetization and electron density as controlled by P doping. In particular, under conditions where the acceptor dopants are activated leading to a decrease in free-electron density, magnetization is enhanced. The result is consistent with hole-mediated ferromagnetism in Mn-doped ZnO, in which bound acceptors mediate the ferromagnetic ordering. Increasing the electron density decreases the acceptor concentration, thus quenching the ferromagnetic exchange. This result is important in understanding ferromagnetism in transition metal doped semiconductors for spintronic devices. [ABSTRACT FROM AUTHOR]

Wide band gap semiconductors such as GaN and ZnO have continued to be at the forefront of spintronics research due to the demonstration of room-temperature ferromagnetism in these materials. A goal of this research is the fabrication of a spintronic device that may provide easy incorporation into existing GaN and ZnO technologies, higher integration density, and less power consumption that its electronic counterparts while achieving similar speeds. The progression of the ferromagnetic metals incorporated into GaN has moved from transition metals to rare earth metals such as the lanthanides. The properties of transition metal-doped ZnO thin films for the two most studied transition metal dopants, namely Mn and Co, are also discussed in this review. [ABSTRACT FROM AUTHOR]

Abstract: Recent efforts on doping ZnO films for charge and spin functionality are reviewed, focusing on chemical doping for charge and spin device formation. Discussion includes the behavior of phosphorus as an acceptor and magnetism in transition metal-doped ZnO. Evidence for p-type behavior in phosphorus-doped (Zn,Mg)O grown by pulsed laser deposition is presented. The magnetic properties of ZnO co-doped with Mn and Sn are also discussed. [Copyright &y& Elsevier]

Semiconducting oxides offer the potential for exploring and understanding spin-based functionality in a semiconducting host material. Theoretical predictions suggest that carrier-mediated ferromagnetism should be favored for p-type material. Cu2O is a p-type, direct wide bandgap oxide semiconductor that may hold interest in exploring spin behavior. In this paper, the properties of Mn-doped Cu2O are described. Activities focused on understanding Mn incorporation during thin-film synthesis, as well as magnetic characterization. The epitaxial films were grown by pulsed-laser deposition. X-ray diffraction was used to determine film crystallinity and to address the formation of secondary phases. SQUID magnetometry was employed to characterize the magnetic properties. Ferromagnetism is observed in selected Mn-doped Cu2O films, but appears to be associated with Mn3O4 secondary phases. In phase-pure Mn-doped Cu2O films, no evidence for ferromagnetism is observed. [Copyright &y& Elsevier]