Growth And Characterization Of Tin Oxide Thin Films And Its Heterojunction Based On Atomic Layer Deposition

Transparent conductive oxides?TCOs?have become promising materials for basic research and application owing to their diversity in electrical,optical and chemical properties.Tin dioxide is a very important wide band gap transparent conductive semiconductor oxide and widely uses in the fields of solar cells,solid-state chemical sensors and electroluminescent diodes.Atomic layer deposition,as a new thin film deposition technology in the 20th century,has the advantage of accurately controlling the thickness of thin films at the atomic scale,which makes it possible to further reduce the characteristic size of CMOS integrated circuits.In this paper,tin oxide thin films were prepared by atomic layer deposition using Tetrakis?dimethylamino?tin and deionized water as precursors at 175?.Tin oxide thin films were annealed at 300,400 and 500?in hydrogen and oxygen atmosphere.The characterization methods of atomic force microscopy,scanning electron microscopy,X-ray photoelectron spectroscopy,ultraviolet-visible spectrophotometer and dielectric spectroscopy were used to analyze the properties of the films.In addition,a SnO₂/Si heterojunction was fabricated.The temperature dependence of the basic parameters of the heterojunction?ideal factor,rectification ratio,barrier height,etc.?were analyzed.The relationship between carrier conduction mechanism at the interface of the heterojunction and temperature and applied voltage was studied in detail.After annealing tin oxide films at different temperatures and atmospheres,we found that the I-V characteristics of the samples annealed in hydrogen atmosphere gradually changed from linear to non-linear with the increase of annealing temperature,and the resistance of the films gradually increased,while the carrier concentration gradually decreased.The curves in oxygen atmosphere are all linear,and the resistance decreases with the increase of annealing temperature.The dielectric properties of tin oxide films show that annealing in hydrogen will lead to the decrease of capacitor and dielectric loss with the increase of temperature.The capacitor and dielectric loss of the sample annealed in oxygen increase with the increase of temperature.The I-V characteristic curves of SnO₂/Si heterojunctions at temperatures ranging from 290 K to 400 K are analyzed.The results show that the ideal factor,rectification ratio and series resistance of SnO₂/Si heterojunctions decrease with the increase of temperature,while the reverse saturated current,knee voltage and barrier height increase with the increase of temperature.We believe that the performance of the heterojunction is improved because the average interface state density of the heterojunction decreases with the increase of temperature.In addition,we found that there are three mechanisms for carrier conduction at the interface of the heterojunction.Carrier conduction mechanisms are mainly thermionic emission and direct tunneling mechanism in high temperature and low pressure region,thermionic emission and Fowler-Nordheim?F-N?tunneling mechanism in high temperature and high pressure region,direct tunneling mechanism in low temperature and low pressure region and F-N tunneling mechanism in low temperature and high pressure region.Compared with ZnO/Si heterojunction,SnO₂/Si heterojunction overcomes the shortcomings of unsaturated reverse current and small rectification.For the first time,the interface carrier conduction mechanism related to temperature and applied voltage of SnO₂/Si heterojunction was studied.We believe that these results will contribute to the understanding of tin oxide films and significantly improve the properties of wide band gap oxide-based heterojunctions.