Investigation On Preparation Of P-type ZnO Films Doped With Indium(Copper)-nitrogen And Their Properties

Zn O is an attractive wide-band-gap semiconductor with a direct band gap of 3.37 e V at room temperature and exciton binding energy as much as 60 me V. Meanwhile, the continuous preparation technology of Zn O single crystal and films accelerate wide application in all fields. However, due to the asymmetry of Zn O doped, the fabrication of high quality stable p-type Zn O is more difficult to obtain than that of n-type Zn O. Moreover, ultraviolet light-emitting of Zn O homogenous p-n junction LED for long time has been not yet reported, indicating that the p–type conductivity of Zn O is still a core problem for Zn O semiconductor materials.In this paper, N-In codoped, Cu doped, and Cu-N codoped Zn O films have been prepared by magnetron sputtering together with N ion implantation technogy. We obtained p-type N-In co-doped Zn O [Zn O:(In, N)] thin films by annealing. Cu doped, and N-Cu co-doped Zn O[Zn O:(Cu, N)] thin films perform room temperature ferromagnetism. By means of Hall test(Hall), Raman spectroscopy(Raman), photoluminescence spectra(PL), X ray photoelectron spectroscopy(XPS) and superconducting quantum interference device(SQUID), the optical, electrical and magnetic properties of N doped Zinc Oxide have been investigated. The main specific contents and results are as follows:①The electrical properties of Zn O:(In, N) films with annealing temperature and time have been studied. The films annealed at 580°C for 25 min keep good p-type conductivity with the hole concentration of 1.27×1018 cm-3, mobility of 2.39cm2?V-1?s-1, and resistivity of 2.06 Ω?cm. I-V curves of p-Zn O:(In, N)-Zn O:In homojunction show obvious rectifying characteristics with the threshold voltage of 2.18 V. Based on experiments and first principles calculation, we further explore the p-type conductive mechanism and stability of Zn O:(In, N) films.The results are:1) Compared to N doped Zn O, In-N co-doping can significantly improve the solid solubility of N in Zn O films. The formation of neutral impurity band of InZn-NO above the valence band maximum(VBM) bring about the relatively shallow acceptor level of N. From temperature-dependence PL analysis, the acceptor ionization energy is deduced about 127 me V.2) In the experiment, the annealing temperature required for p-type conductivity of Zn O:(In, N) films decreased significantly due to the incorporation of In. CI-nudged elastic band(NEB) simulation show that, compared with the diffusion barrier of N(2.1e V) in Zn O, the Ni diffusion barrier(1.3e V) in nearest neighboring InZn in Zn O decreased. Based on XPS analysis of, complexe defects(N2-O)O and(N-O)O easily formed in Zn O:(In, N) films begin to dissociate at 550 and 580°C, respectively.3) The results from the tracking sample showed that the p-type conductivity of the sample annealed at 580±10°C for 10~25min maintain relative stability. Especially, a few samples can keep the carrier order of 1017cm-3 even for two years. According to the existing technological parameters, preparation of p-type Zn O film with good properties can be repeated. A small amount remaining Ni in Zn O film easily bond with NO at room temperature, acting as the donor compensation. Therefore, as far as possible to eliminate the remaining Ni is the key to ensure the stability of p conductive Zn O thin films.②Zn1-xCuxO and Zn1-xCuxO:N(x=0.5%~5%) films were prepared on quartz substrates by RF magnetron sputtering and ion implantation technology. The results are:1) With the increasing concentration of Cu doped Zn O thin film, carrier concentration of the film decreased significantly. Both Zn1-XCuXO(x=0.01) films and Zn1-XCuXO:N(x=0.005) films annealed at 550°C for 30 min in the Ar atmosphere show p-type conducvity, corresponding to concentration of 2.371×1015cm-3 and 9.155×1016 cm-3, respectively. When Cu concentration was more than 2%, regardless of the Cu doped Zn O and Cu-N doped Zn O thin films are basic insulation.2) Zn1-xCuxO(x=2%~5%) films have room temperature ferromagnetism. However, the Zn O:Cu thin films annealed in argon atmosphere at 580 °C for 30 min show from ferromagnetic to paramagnetic because the formation of a large number of oxygen vacancies in the films by annealing.3) N ion implantation can improve the room temperature ferromagnetism of Zn O:Cu thin films by occuping the oxygen vacancies or substituting for lattic O in Zn O:Cu films due to the coupling between Cu 3d and N 2p states.4) The Zn O:Cu films at high dose of N+ ion implantation will become saturated magnetization as the doping concentrationthe of Cu is 5at%.③The investigation on the electronic and magnetic properties of Zn O monolayer system with intrinsic defects(VO, VZn) or Cu/N dopant based on first-principles theory shows that:1) The Zn25O24 nanosheet system is not magnetic, while the total magnetic moment of Zn24O25 is 1.6μB, which originates from spin polarization of the nearest neighbor O 2p states at the Fermi level. Furthermore, two VZn in the Zn34O36 nanosheet system favor to aggregate energetically and exhibit ferromagnetic coupling.2) Cu doped Zn O nanosheet system has characteristics of the spin-polarized due to the coupling between Cu 3d and O 2p states. However, two CuZn atoms in the Zn30Cu2O32 nanosheet favor to aggregate energetically and exhibit antiferromagnetic coupling. The ground state of Zn32O30N2 nanolayer is also antiferromagnetic and two N locate on the nearest neighboring lattic O sites. Zn32O30N2 nanolayer performs paramagnetic. It is found that Cu-N codoped Zn30Cu2O31 N nanosheets show room temperature ferromagnetism, easily forming the complex of CuZn-NO-CuZn with the total magnetic moment for the complex is 1.85μB(MCu=0.62μB, MN =0.61μB).In this dissertation, we not only successfully prepare p-type Zn O thin films, but also find the change law of p-type conductivity in Zn O:(In, N) films. Furthermore, the effect of the remaining interstitial Ni on the stability of p-type Zn O thin films is first proposed, which provides an effective method of fabricating stable p-type Zn O film. In addition, the first-principles calculations indicate that Cu-N codoped monolayer Zn O is expected to achieve room temperature ferromagnetic, which can offer a theoretical reference for the experimental preparation and research on monolayer Zn O.