ACTIVATION AND DEACTIVATION OF ROOM TEMPERATURE FERROMAGNETISM IN ZnO FILMS

In this paper, we report the activation and deactivation of room temperature ferromagnetism in pure and V doped ZnO (Zn0.95V0.05O) films upon surface functionalization with thiol. The thiol functionalized pure ZnO and Zn0.95V0.05O films has been investigated with X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), temperature programmed desorption (TPD) and vibrating sample magnetometer (VSM) measurements. The presence of S 2p(3/2) peak about 163.5 eV implies that the formation of Zn-S bonds which in turn leads to the reduction of oxygen vacancies. PL spectra of thiol functionalized pure ZnO and Zn0.95V0.05O films show quenching of visible emission in comparison with the unfunctionalized ZnO films. TPD measurements show that the adsorption of thiol on ZnO surface is stable upto 480 K. On vacuum annealing of the thiol functionalized films above 480 K, desorption starts and gets completely desorbed about 535 K. The room temperature VSM measurements reveal clear signature of ferromagnetic behavior in the functionalized ZnO films. The disappearance of ferromagnetic behavior after vacuum annealing at 550K confirms the observed ferromagnetic behavior in thiol functionalized ZnO films is due to the strong interaction between the ZnO host and thiol molecules.