A series of Cr-doped ZnO micro-rod arrays were fabricated by a spray pyrolysis method. X-ray diffraction patterns of the samples showed that the undoped and Cr-doped ZnO microrods exhibit hexagonal crystal structure. Surface morphology analysis of the samples has revealed that pure ZnO sample has a hexagonal microrod morphology.From X-ray photoelectron spectroscopy studies, the Cr 2p3/2 binding energy is found to be 577.34 eV indicating that the electron binding energy of the Cr in ZnO is almost the same as the binding energy of Cr 3+ states in Cr 2 O 3 .The optical band gap E g decreases slightly from 3.26 to 3.15 eV with the increase of actual Cr content from x = 0.00 to 4.63 at % in ZnO. Photoluminescence studies at 10 K show that the incorporation of chromium leads to a relative increase of deep level band intensity. It was also observed that Cr doped samples clearly showed ferromagnetic behavior; however, 2.49 % Cr doped ZnO showed remnant magnetization higher than that of 1.07 % and 4.63 % Cr doped samples, while 4.63 % Cr doped ZnO samples had a coercive field higher than the other dopings.

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ZnO thin films are deposited by radio-frequency magnetron sputtering on thermally grown SiO2 on Si substrates. Pt/Au contacts are fabricated by standard photolithography and lift-off in order to form a metal-semiconductor-metal (MSM) photodetector. The dark current of the photodetector is measured as 1 pA at 100 V bias, corresponding to 100 pA/cm2 current density. Spectral photoresponse measurement showed the usual spectral behavior and 0.35 A/W responsivity at a 100 V bias. The rise and fall times for the photocurrent are measured as 22 ps and 8 ns, respectively, which are the lowest values to date. Scanning electron microscope image shows high aspect ratio and dense grains indicating high surface area. Low dark current density and high speed response are attributed to high number of recombination centers due to film morphology, deducing from photoluminescence measurements. These results show that as deposited ZnO thin film MSM photodetectors can be used for the applications needed for low light level detection and fast operation.