Study On Preparation Of Low Dimensional Hexagonal Boron Nitride By Chemical Vapor Deposition

In recent years,low-dimensional materials have become a very popular research content.Low-dimensional materials often have their unique properties,the relevant application value is reflected in many scientific research fields,which has attracted the attention of countless scientific researchers.Hexagonal boron nitride(hBN)is one of many low-dimensional materials.Its surface is atomically smooth,has no dangling bonds,has strong thermal stability,chemical inertness,oxidation resistance,electrical insulation,high thermal conductivity,and also has unique photoelectric properties.Such excellent performance makes hexagonal boron nitride have far-reaching application value in many fields.At the same time,the preparation of high-quality hexagonal boron nitride films has become a hot research content.The preparation of low-dimensional hexagonal boron nitride film has successively experienced the development from mechanical peeling,liquid phase peeling,physical vapor deposition and chemical vapor deposition.Among them,chemical vapor deposition(CVD)has gradually become the most common and most promising preparation method.In this experiment,we mainly explored the process of preparing low-dimensional hexagonal boron nitride by low-pressure chemical vapor deposition(LPCVD).First,the surface roughness and crystallinity of the metal copper foil are improved by the annealing process of the copper substrate,and a smooth Cu(111)substrate surface is obtained.Next,ammonia borane is used as a raw material to grow hexagonal boron nitride films,and the research is carried out through a combination of experiment and characterization.The X-ray photoelectron spectroscopy(XPS)of the film showed that the peak positions of B 1s and N 1s are located at 190.47 e V and398.14 e V,respectively,and the atomic ratio of B to N reaches 1.10:1.Then,the traditional PMMA transfer technology was used to transfer the 1.5×1.5 cm size hexagonal boron nitride film to the surface of sapphire and Si O₂/Si substrate for further characterization.The thickness of the film measured by the atomic force microscope is about 10.5 nm.Ultraviolet-visible absorption spectroscopy measured that the film has a strong absorption near 210 nm in the deep ultraviolet region,and the band gap is calculated to be near 5.9 e V,which proves good crystalline quality of the film.In addition,the effects of various experimental parameters on the results were explored,and the effects of growth pressure,growth temperature,growth time,ammonia borane heating temperature on the film results were studied through the controlled variable method.Finally,the best process conditions for the growth of hexagonal boron nitride films by low-pressure chemical vapor deposition are obtained.In addition,by comparing the breakdown voltage of the film under different growth conditions,it is confirmed that the thickness of the hBN film increases with the increase of the growth time and the increase of the source heating temperature.In order to further confirm the photoelectric properties of the film,this experiment also produced a hexagonal boron nitride film ultraviolet photodetector device.The interdigital electrode of metal gold was vapor-deposited on the surface of the hexagonal boron nitride film by means of thermal evaporation,and the finger pitch and finger width were both 100?m.The produced UV photodetector has tested the light current and dark current of the detector through a 2410 digital source meter and a light source with a wavelength of 184.9 nm.Under a bias of 2 V,the photocurrent reaches 1 n A,and the dark current is up to 300 p A.The good performance response of the detector also proves the quality of the hexagonal boron nitride film.