氮化硼薄膜的厚度对场发射特性的影响

Effect of Thickness of Thin BN Films on Field Emission Characteristics

利用射频磁控溅射方法,在n型(100)Si基底上沉积了不同厚度(54～124nm)的纳米氮化硼(BN)薄膜.红外光谱分析表明,BN薄膜结构为六角BN(h-BN)相(1380cm-1和780cm-1)结构.在超高真空系统中测量了不同膜厚的场发射特性,发现阈值电压随着厚度的增加而增大.厚度为54nm的BN薄膜样品阈值电场为10V/μm,当外加电场为23V/μm时,最高发射电流为240μA/cm2.BN薄膜场发射F-N曲线表明,在外加电场作用下,电子隧穿了BN薄膜表面势垒发射到真空.

Nanometer boron nitride(BN) thin films with various thickness(54~124 nm) were fixed on the (100)oriented surface of nSi(ρ=0008~002 Ω·m) by r.f. magnetic sputtering physical vapor deposition(PVD). There are only two absorption peaks of the hexagonalBN(hBN) at about 1 380 cm-1 and 780 cm-1 in the FTIR spectra of the BN thin films. The field emission characteristics of the thin BN films were measured in a super high vacuum system. It was found that the field emission characteristics of the thin BN films depend evidently on the thickness of the films. A turnon electric field as low as 10 V/μm is obtained for the ～54 nmthick BN film, and the emission current density is estimated to be higher 240 μA/cm2 at an electric field of 23 V/μm. It is shown by FN curves that the electrons emitted from BN penetrate through the potential barrier at the surface of the BN thin film to vacuum tunneling under the exterior electric field action.