物理学报2016，Vol.65Issue(11)：116801-1-116801-8,8.DOI:10.7498/aps.65.116801
铜箔上生长的六角氮化硼薄膜的扫描隧道显微镜研究∗
Scanning tunneling microscopy study of h-BN thin films grown on Cu foils
摘要
Abstract
Analogous to graphite, hexagonal boron nitride (h-BN) has a layered structure composed of boron and nitrogen atoms that are alternatively bond to each other in a honeycomb array. As the layers are held together by weak van der Waals forces, h-BN thin films can be grown on surfaces of various metal crystals in a layer-by-layer manner, which is again similar to graphene sheets and thus attracts a lot of research interests. In this work, scanning tunneling microscope and spectroscope (STM and STS) were applied to the study of an h-BN thin film with a thickness of about 10 nm grown on Cu foil by means of chemical vapor deposition. X-ray diffraction from the Cu foil shows only one strong peak of Cu(200) in the angle range of 40◦–60◦, indicating that the Cu foil is mainly Cu(100). After sufficient annealing in an UHV chamber, the h-BN film sample is transferred to a cooling stage (77 K) for STM/STS measurement. Its high quality is confirmed by a large-scale STM scan that shows an atomically flat topography. A series of dI/dV data taken within varied energy windows all exhibit similar U shapes but with different bottom widths that monotonously decrease with the sweeping energy window. The d I/d V curve taken in the energy window of [−1 V,+1 V] even shows no energy gap in spite that h-BN film is insulating with a quite large energy gap of around 6 eV, as observed in a large-energy-window d I/d V curve (from −5 V to +5 V). These results indicate that the STM images reflect the spatial distribution of tunneling barriers between Cu(100) substrate and STM tip, rather than the local density of states of the h-BN surface. At high sample biases (from 4 V to 1 V), STM images exhibit an electronic modulation pattern with short range order. The modulation pattern displays a substructure in low-bias STM images (less than 100 mV), which finally turns to the (1×1) lattice of h-BN surface when the sample bias is extremely lowered to 3 mV. It is found that the electronic modulation pattern cannot be fully reproduced by superimposing hexagonal BN lattice on tetragonal Cu(100) lattice, no matter what their relative in-plane crystal orientation is. This implies that the electronic modulation pattern in the STM images is not a Morié pattern due to lattice mismatch. We speculate that it may originate from spatial distribution of tunneling barrier induced by adsorption of H, B and/or N atoms on the Cu(100) surface in the CVD growth process.关键词
氮化硼/隧穿势垒/扫描隧道显微镜Key words
boron nitride/tunneling barrier/scanning tunneling microscopy引用本文复制引用
徐丹,贾金锋,殷俊,孙昊桦,王观勇,钱冬,管丹丹,李耀义,郭万林,刘灿华..铜箔上生长的六角氮化硼薄膜的扫描隧道显微镜研究∗[J].物理学报,2016,65(11):116801-1-116801-8,8.基金项目
国家重点基础研究发展计划(批准号:2013CB921902,2012CB927401,2013CB932604,2012CB933403)、国家自然科学基金(批准号:11521404,11134008,11574201,11574202,11504230,51472117,51535005)、上海市科委科技基金(批准号:15JC1402300,14PJ1404600)和江苏省自然科学基金(批准号：BK20130781)资助的课题.@@@@* Project supported by the National Basic Research Program of China (Grant Nos.2013CB921902,2012CB927401,2013CB932604,2012CB933403), the National Natural Science Foundation of China (Grant Nos.11521404,11134008,11574201,11574202,11504230,51472117,51535005), Shanghai Committee of Science and Technology, China (Grant Nos.15JC1402300,14PJ1404600), and Jiangsu Province Natural Science Foundation, China (Grant No. BK20130781) （批准号:2013CB921902,2012CB927401,2013CB932604,2012CB933403）
