沉积气压对氮化硼薄膜场发射特性的影响

Influence of Deposition Pressure on Field Emission Characteristics of Boron Nitride Films

利用等离子体增强脉冲激光沉积系统,在n型Si(100)基底上沉积了不同沉积气压下的纳米BN薄膜,利用红外光谱(FTIR)对BN薄膜进行了表征。通过原子力显微镜(AFM)观察了薄膜的表面形貌。在超高真空(<5.0×10-7Pa)情况下测量了薄膜的场致发射特性。实验结果表明,沉积气压对BN薄膜的场发射特性影响很大。BN薄膜的阈值电场随着沉积气压的升高而升高,发射极限电流随着沉积气压的升高而较小,但耐压特性提高。沉积气压为2Pa时沉积的BN薄膜的场发射的阈值电场最低,为12V/μm,当电场升高到27V/μm时,场发射电流密度为140.6μA/cm2;当沉积气压升高到5Pa时,阈值电场升高为26V/μm,当电场升高到59V/μm时,发射电流密度为187.5μA/cm2;沉积气压升高到15Pa时的样品的阈值电场已经高达51V/μm。所有BN薄膜的F-N曲线都符合F-N理论,表明电子发射是通过隧穿表面势垒完成的。

Orthorhombic boron nitride （o-BN） films were prepared on n-Si（100） substrate by plasmaenhanced pulsed laser deposition （PE-PLD） at different deposition pressure. The films were characterized by Fourier transform infrared （FTIR） spectroscopy and atomic force microscopic （AFM）. The field emission characteristics of the BN thin films were measured in an ultrahigh vacuum system （〈5.0 × 10^-7 Pa）. The results showed that pressure is an important influencing factor for the field emission characteristics of BN films, the threshold electric field and the withstand voltage of the BN films increases with increasing of deposition pressure, and the highest emission current density decreases with increasing of deposition pressure. A threshold electric field of 12 V/um and the highest emission current density of 140.6 mA/cm^2 at an electric field of 27 V/um were obtained for the film at deposition pressure 2 Pa, a threshold electric field of 26 V/um and the highest emission current density of 187.5 mA/cm^2 at an electric field of 59 V/um were obtained for the film at deposition pressure 5 Pa, and a threshold electric field of 51 V/um was obtained for the film at deposition pressure 15 Pa. The Fowler-Nordheim plots show that electrons are emitted from BN to vacuum by tunneling through the potential barrier at the surface of BN thin films.