Characterization and optoelectronic properties of p-type N-doped CuAlO2 films

Abstract

This letter reports a technique for increasing the carrier concentration and the conductivity of the p-type CuAlO2 through doping the material with nitrogen. The x-ray photoelectron spectroscopy and the optical band gap analyses suggested that the nitrogen atoms occupying the interstitial sites of the delafossite structure provided the p-type CuAlO2 with an impurity energy level in the energy gap. It was also found that the N-doped CuAlO2 film had its optimum conduction properties when the dopant level reached 1.1 at. %. Here, the carrier concentration was raised from 4.81x10(16) in the undoped film to 2.13x10(17) cm(-3) in the doped film, and the corresponding film's conductivity was increased from 3.8x10(-2) to 5.4x10(-2) (Omega cm)(-1), as compared with the undoped CuAlO2 film. (C) 2007 American Institute of Physics

Preparation and properties of transparent conductive N-doped CuAlO2 films using N2O as the N source

“…It is obvious that the film using 15 % N 2 O flow ratio reaches the optimum crystallinity. Due to the similar atomic radii of N and O, the delafossite structure is hardly affected when N is doped into the CuAlO 2 lattice [10]. This has been confirmed by XRD patterns in which all the peaks corresponding to classical delafossite structure are stable and hardly changed after N-doping.…”

“…In our work, the accepter impurity N is believed to be another main factor for the conductivity of N-doped CuAlO 2 films. The nonstoichiometric defects for N-doped CuAlO 2 films can be represented by the following equations [10,23]: (3) shows the electrical mechanism for acceptor N in the oxygen site. Compared with the equation (2), when a N atom enters into CuAlO 2 lattice, an extra hole carrier will be created, which is considered as the main reason for the increasing conductivity with the increase of N 2 O flow ratio.…”

“…Therefore, as p-type impurity for CuAlO 2 , N atoms in the lattice position is ionized and formed N 3-, compared with O 2-in lattice, which can contribute an extra hole to increase the carrier concentration. In addition, the interval of the lattice in this classical delafossite structure could also be an ideal site for accepter N [10].…”

Structural, optical and electrical properties of delafossite CuGaO2films grown by sol-gel method

“…[1] In the delafossite compounds, the structure CuMO 2 (M=Al, Ga, and In) can be visualized as consisting of two alternate layers: a planar layer of Cu cation in a triangular pattern and a layer of edge-sharing MO 6 octahedra flattened with respect to the c-axis. [1,2] Although most delafossite films have been prepared by vacuum based technologies, [3][4][5] there are only a few reports on the sol-gel synthesis of p-type delafossite films in recent years. [6,7] This is because the instability of Cu + and the sensibility of the oxygen partial pressure.…”

Energy Generation: Solar Energy

“…For a long time, there has been no agreement either on the origin of the p-type conductivity or on the electronic band gap of the pure crystal. Measurements of the direct optical band gap (E dir g ) of CuAlO 2 fall in the range from 2.9 eV to 3.9 eV [19,20,136,[139][140][141][142][143][144][145][146][147][148][149], with most values in the interval 3.4-3.7 eV. These experiments also yield a large dispersion of indirect gaps (E ind g ), from 1.65 eV to 2.1 eV, with one experiment measuring 2.99 eV [146].…”