Low dimensional (nanowall) ZnO structures were prepared by a two-step growth method with oxygen-plasma-assisted molecular beam epitaxy, where the as-grown film was first engraved on a porous template using the oxygen plasma and then the ZnO nanowalls were grown on the template. The resonance Raman spectra showed the surface mode. A morphology model was proposed on the basis of the scanning electron microscopy patterns and this mode. The room and low temperature photoluminescence showed that the nanowalls had intense ultraviolet emission properties, which benefited from the low dimensional structure with few defects.

The electronic structure of the layered ternary carbides Ti2SnC and Ti2GeC has been investigated by means of ab initio linear combination of atomic orbital calculations. The calculated band structure shows that the electrical conductivity for both Ti2SnC and Ti2GeC is metallic and anisotropic with a high density of states at the Fermi level. The electrical conductivity of Ti2SnC is, however, higher than that of Ti2GeC. The major factors governing the electronic properties are {pd} hybridization from Ti 3d and C 2p states. Compared to the structure of TiC, the presence of Sn or Ge changes the Ti-C-Ti-C covalent bond chain into a Ti-C-Ti-Sn or Ti-C-Ti-Ge bond chain through its reaction with Ti, forming the layered structure.

A lithium (Li) and nitrogen (N) dual-doped p-type ZnO film (ZnO : (Li,N)) was deposited on c-plane sapphire by RF-magnetron sputtering of Zn–2 at.% Li alloy using mixed gases of oxygen and nitrogen and then annealing in N2 flow. It has a carrier concentration of 3.07 × 1016 cm−3 and Hall mobility of 1.74 cm2 V−1 s−1. XPS measurement shows that there are LiZn–N complexes in the p-type ZnO : (Li,N), which are demonstrated by photoluminescence measured at various temperatures and different excitation powers to be acceptors and responsible for p-type conductivity of the ZnO : (Li,N). The optical level of the LiZn–N complex acceptor is estimated to be about 126 meV by measurement of emission energy of free electron to the acceptor level.

Li-doped p-type ZnO was fabricated by heat treatment of Zn-Li alloy film with 2 at% Li on a quartz substrate in N 2 flow at 500 • C for 2 h, and then in O 2 flow at 700 • C for 1 h. The room-temperature resistivity was measured to be 678.34 cm with a Hall mobility of 1.03 cm 2 V −1 s −1 and a carrier concentration of 8.934 × 10 15 cm −3 . Three emission peaks centred at 3.347, 3.302 and 3.234 eV are observed in the photoluminescence spectrum measured at 12 K and are due to neutral acceptor-bound exciton emission, conduction band to acceptor level transition and donor-acceptor pair recombination emission, respectively. The p-type conduction of the Li-doped ZnO may be attributed to the formation of a Li Zn -N complex acceptor. The optical level of the acceptor is estimated to be about 137 meV. The mechanism of formation of the Li-doped p-type ZnO is discussed in the present work.