Study On The Growth And Properties Of Mg-C-O-H Films

With the development of the aerospace photoelectric system, infrared transparent and conductive films have been brought into focus. Infrared transparent and conductive films not only can make the front detector to capture infrared signals, but also protect detector against interference by electromagnetic radiation. However, according to the Drude’s free-electron theory, it is very hard to have both optical and electrical properties. Therefor it is particularly important to solve the contradiction between optical and electrical properties.In this paper, we used a two-step method to prepare Mg-C-O-H films. Firstly, MgxCy films were prepared by magnetron co-sputtering method. Secondly Mgx-Cy films react with water vapor in the high pressure and high temperature autoclave. By discussing the effect of different C target sputtering power, substrate temperature, temperature and time of annealing on films structure, surface morphology and chemical elements, obtained the optimizing way to produce the best properties of Mg-C-O-H films.The films structure, surface morphology and chemical elements were affected by the different sputtering power of C target. With the increasing of C target sputtering power, the crystallinity of films decrease and the surface roughness increase. Due to the increased of carrier concentration, the visible light transmittance decrease with the increase in sputtering power of C target. However the visible light transmittance were also greater than 80%. Because of increasing of carrier concentration, the optical bandgap of Mg-CO-H films are about 4.04~6.87 e V. When the sputtering power of C target is 120 W show resistivity about 69.7 Ω·cm, and carrier concentration about 2.4×1015 cm-1, the films of Mg-C-O-H reach the best electrical properties. But the electrical properties, under different C target sputtering power, of Mg-C-O-H films change little. When Mgx-Cy films reacted with water vapor, the C segregated with Mg atoms. The poor compatibility of C and Mg is responsible for this phenomenon.We can see that when changing the substrate temperature, the structure of Mgx-Cy films will be altered. Because of C atoms integrating into the films crystalline structure, the X-ray diffraction peaks of Mgx-Cy films shift towards low diffraction angle. With the increasing of substrate temperature, the preferred growth orientations(001) transformed into(101) and(110). With the increasing of substrate temperature, Mg-C-O-H films resistivity decreased, the carrier concentration and mobility increased. Mg-C-O-H films with substrate temperature of about 400℃ show low resistivity of about 4.086 Ω·cm, high electron mobility of about 49.18 cm2V-1s-1 and high carrier concentration of about 3.11×1016 cm-3. With the increasing of substrate temperature, the visible light transmittance of Mg-C-O-H films change little. Because of increasing of substrate temperature, the carrier concentration increase gradually and the infrared transmittance decreases gradually. But the transmittance of Mg-C-O-H films are over 70% in 3~5 μm and 8~10 μm.When Mg-C-O-H films annealed under different temperature and time, the optical and electrical properties was changed. Mg-C-O-H films with annealing temperature and time of about 140℃ and 1.5 h show low resistivity of about 0.348 Ω·cm, high carrier concentration of about 2.98×1017 cm-3 and high electron mobility of about 58.38 cm2V-1s-1. And the visible transmittance of Mg-C-O-H films are over 85%, infrared transmittance is greater than 70%.