The Microstructure And Optical Properties Of NC-Ge/SiO₂Thin Multi-films

Si-based nano-materials have been widely used in the preparation of device and the photovoltaicdue to their advantages such as larger light absorption coefficient, specular conductivity, carriermobility and optical band gap. Consequently, it is one of the hot spots of present study. The goal ofthis paper was to obtain nc-Ge/SiO₂multilayer film with good performance and stability viamagnetron sputtering technology. We took Ge/SiO₂multilayer structure as the research object,meanwhile, characterized the properties including morphology, optical property and mechanicalproperty via the measurement of XRD, Raman, FESEM, steps instrument, UV-Vis and scratch test.Furthermore, we investigated the influence of the Ge layer thickness, cycle number and annealingprocess on the microstructure, optical properties and the mechanical properties of Ge/SiO₂multilayerfilm, and researched the structure and performance of the B doping Ge/SiO₂multilayer.It was the cycle number and Ge layer thickness that influenced the structure and opticalproperties of Ge/SiO₂multilayer film. The as-deposited Ge/SiO₂multilayer was microcrystal structurewhich was constituted by particles and was well periodical. As the augment of Ge layer thickness, thesurface roughness got lower firstly and then increased; when the Ge layer thickness was8.5nm, thesurface roughness reached to the minimum. The elevation of film cycle number brought about theelevation of surface roughness, and the amplitude reduced. The increase of both cycle number and Gelayer thinness resulted in the red shift of absorption edge.Annealing process could enhance the crystallization properties, surface morphology and opticalperformance of （Ge/SiO₂）₁₅. The crystallinity became stable for the annealed sample at500℃, whenthe temperature rose to600℃, the crystal size increased. The crystal size increased accompanyingwith the prolongation of annealing time, moreover, the annealing time influenced the crystallizationproperties significantly. With the increase of annealing temperature or annealing time, the surfaceroughness presented a tendency from decrease to increase, so did the adhesion strength between filmand substrate; the optical band gap gradually decreased. In addition, thin film possessed optimalcomprehensive properties.B doping had an impact on the optical absorption performance and annealing performance of（Ge/SiO₂）₁₅in a degree. After doping of element B, the optical absorption edge occurred to red shift.The results of annealing process of （Ge:B/SiO₂）₁₅film demonstrated that crystallization emerged inthe film when the annealing temperature was500℃, and the crystal size and surface roughnessincreased along with the elevation of annealing temperature. However, compared with the （Ge/SiO₂）₁₅ film upon the same condition, the crystal size was smaller, and we argued the B element could inhibitthe growth of crystal. With the increase of annealing temperature, the optical band gap of （Ge:B/SiO₂）₁₅thin film had the trend of decrease, but the decline range was not obvious. With thetemperature rise, the adhesion first increased, then decreased.