Physical Properties Of F And Al Co-Doped ZnO Thin Films Prepared By Laser Molecular Beam Epitaxy

Transparent conductive electrodes(TCEs)are one of the most important components of many optoelectronic devices such as solar cells,organic light emitting diodes(OLEDs)and large panel displays.Comparing with the emerging metal nanowire networks and graphene based TCEs,traditional metallic oxide based TCEs like ITO,AZO and FTO have many advantages like high transmittance,tunable electrical properties and mature processing techniques,and still dominates the markets.Among those metallic oxide based TCEs,AZO are the cheapest and the most environmentally friendly,making AZO one of the most promising candidate.However,comparing with the most widely used ITO,AZO exhibits a higher resistivity and lower thermal stability in oxidizing atmosphere,which sincerely limits AZO's applications.To searching for proper solutions for these two problems,in paper the F and Al co-doped Zn O(AFZO)TCEs were prepared by laser molecular beam epitaxy(LMBE)technique in combination with various annealing processes.The optical and electrical properties of AFZO and AZO under different annealing conditions were compared in order to discuss the nature and the formation of defects in AZO as well as the effects of F doping in AZO.The main results obtained are as follows:1?The samples were prepared by LMBE technique.Al F3 and Zn O powders were mixed and molded and then calcined to obtain the high quality target.AFZO and AZO thin films were prepared on the c-plane sapphire at 300 oC with good transparency and conductivity.In comparison with AZO prepared at the same conditions,AFZO films exhibit better electrical parameters.2?The crystal structure and photoelectric property of AFZO annealed in the vacuum and the air were studied,respectively.After carefully comparison between the electrical properties of AZO and AFZO,we made an assumption that the introduction of fluorine is able to enhance the electrical properties and the thermal stability in the oxygen atmosphere of AZO.Under the vacuum annealing conditions,the improvement of electrical properties of AFZO is more obvious.Under vacuum annealing conditions,the minimum resistivity of AFZO is 1.7×10-4 ?cm with the mobility as high as 61.6 cm2V-1s-1.And under air annealing conditions,the minimum resistivity of AFZO is 1.88×10-4 ? cm with the mobility as high as 59.6 cm2V-1s-1.3?Based on the different electrical properties and stability of AZO and AFZO before and after air annealing,we put forward that the presence of acceptor-like Zn vacancies VZn is mainly responsible for the degradation of AZO,while proper F doping can effectively restrain the VZn from forming.The effect of F doping on VZn had been verified by comparing the emission intensity of defects in the photoluminescence spectra and the change of electrical properties of thin films after annealing under N2/H2 mixture and Zn atmosphere.The variation of electrical properties of F doped Mg Zn O with air annealing temperatures was also used as a proof of our assumption.