Combinatorial laser molecular-beam epitaxy method was employed to fabricate epitaxial ZnO thin films doped with all the 3d transition metal (TM) ions in a high throughput fashion. The solubility behavior of TM ions was discussed from the viewpoints of the ionic radius and valence state. The magneto-optical responses coincident with absorption spectra were observed for Mn- and Co-doped samples. Cathodoluminescence spectra were studied for Cr-, Mn-, Fe-, and Co-doped samples, among which Cr-doped ZnO showed two sharp peaks at 2.97 eV and 3.71 eV, respectively, at the expense of the exciton emission peak of pure ZnO at 3.25 eV. Different magnetoresistance behavior was observed for the samples codoped with n-type carriers. Ferromagnetism was not observed for Cr- to Cu-doped samples down to 3 K.

S-doped ZnO (ZnO:S) film was fabricated by supplying ZnS species from laser ablation of a ZnS target during ZnO growth. Variations of lattice constants and band gaps with respect to S content did not follow Vegard’s law. The ZnO:S film showed semiconducting behavior with lower activation energy and resistivity than those of ZnO owing to higher carrier concentration. Despite the absence of magnetic elements, the large magnetoresistance amount of 26% was observed at 3 K from ZnO:S film.

Combinatorial laser molecular-beam epitaxy method was employed to fabricate epitaxial Zn1−xMnxO thin films in a high throughput fashion. Local structures around Mn were investigated for these c-axis-oriented epitaxial films by fluorescence x-ray absorption fine structure measurements. It was shown that Mn substitutionally replaces Zn in Zn1−xMnxO (x<0.22) films. Well-structured blue and ultraviolet cathodoluminescence peaks corresponding to the intra-d-shell transitions of Mn2+ were observed, especially for smaller x. The luminescence is quenched rapidly as x is increased. By comparing the relative absorption strength per mole Mn2+ with the statistical probability of isolated Mn2+, it was concluded that the quick decrement of isolated Mn2+ with increasing x is responsible for the severe suppression of the blue and ultraviolet luminescence.

Co-doped ZnO(Zn1−xCoxO) and Co, Al codoped ZnO(Zn1−xCoxO:Al) films were grown on c-plane sapphire (0001) substrates by pulsed laser deposition using a KrF excimer laser. In order to enhance homogeneous substitution of Co2+ for Zn2+ in the ZnO film, an alternating deposition (AD) method was employed for doping. ZnO films doped with the same elements were grown without employing the AD method under the same fabrication conditions to compare with the corresponding AD films. Despite Co incorporation, the Zn1−xCoxO film by AD methods showed better crystallinity than pure ZnO film. Also, the crystallinity of Zn1−xCoxO:Al films by AD methods was better than those of Zn1−xCoxO and ZnO:Al films by conventional doping methods. Root mean square roughnesses of the films by AD methods were less than 1.6 nm. Absorption peaks caused by d–d transitions were observed at 1.88, 2.01, and 2.19 eV in Zn1−xCoxO films. The electric conductivity of Zn1−xCoxO:Al film by AD methods was comparable to that of ZnO:Al film by conventional methods in spite of Co doping and lower Al concentration.

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