Modeling And Simulation Of Amorphous Silicon Base On First Principle Theory

Amorphous silicon always play an important role in semiconductors materials sciences. A lot of effort has been devoted in the research of pure amorphous silicon. Due to the more stable structure, the research is then focused on hydrogenate amorphous silicon. New material brings new challenges. Compared with crystalline silicon, the biggest advantage of amorphous silicon is the production technology。 The a-Si:H film can be deposited homogeneous on a large area, through the preparation technology like plasma enhanced chemical vapor deposition. Although devices based on a-Si:H are widely used, some of the properties are still not fully understood. A lot of work has been done on the simulation based on first principle theory of regular crystals, but for irregular structure like continuous random network of amorphous silicon, there is still much work to do. In this paper, we studied the modeling of amorphous silicon using first principle theory.The preparation means of a-Si:H is presented and the Experimental conditions of our lab. A brief introduction of the testing methods and devices are listed. The result had been given during in the paperA model contains 64 Si atoms and 8 H atoms was built first. Through “cool of the liquid” method, the crystalline silicon was converted into amorphous structure. During the modeling process, three kinds of cooling rate were introduced. Then different structure properties are listed for the purposes of comparison. Cooling rate sample performs better in reproducing amorphous structure. In order to study the size of the model, a supercell of 216 Si atoms and 27 H atoms was built and compared with the small models. The results are similar.To calculate the optical properties of a-Si:H model,other five small models were built in the slow cooling rate, with the model of Fast/Normal cooling rate. Then we calculate the optical properties: absorption, IR spectra, refractive index and extinction Coefficient. Again,it was proved that the sample of slow cooling rate is more close to the amorphous silicon.