Characterization of the natural barriers of intergranular tunnel junctions:: Cr2O3 surface layers on CrO2 nanoparticles
Characterization of the natural barriers of intergranular tunnel junctions:: Cr2O3 surface layers on CrO2 nanoparticles
复制标题
DOI：
10.1063/1.1320845
复制
发表时间：
2000-10-30
影响因子：
4
通讯作者：
Diebold, U
中科院分区：
文献类型：
--
作者：
Dai, JB;Tang, JK;Diebold, U
冷压制的二氧化铬粉末由于晶粒间的隧道效应而表现出较大的负磁阻。由针状纳米颗粒制成的粉末在5k下表现出约28%的MR。电阻率的温度依赖性表明，低温下的电导率主要是由库仑阻滞晶间隧穿引起的。在这封信中，我们报告了使用透射电子显微镜，x射线衍射（XRD）和x射线光电子能谱（XPS）对晶间隧道势垒的微观结构的直接观察和表征。在二氧化钛粉末表面形成了一层厚度为1 ~ 3nm的极薄天然氧化层。通过XPS和XRD分析，确定了该表面层的组成和晶体结构为Cr2O3。致密均匀的Cr2O3表面层在cr2粉末压坯中起着理想的隧道屏障作用。(C) 2000年美国物理研究所。[s0003 - 6951(00) 00344 - 2]。
Cold-pressed powder compacts of CrO2 show large negative magnetoresistance (MR) due to intergranular tunneling. Powder compacts made from needle-shaped nanoparticles exhibit MR of about 28% at 5 K. Temperature dependence of the resistivity indicates that the Coulomb blockade intergranular tunneling is responsible for the conductance at low temperature. In this letter we report direct observation and characterization of the microstructure of the intergranular tunnel barriers, using transmission electron microscopy, x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). A very thin native oxide layer with a thickness of 1-3 nm on the surface of CrO2 powders has been observed. The composition and crystal structure of this surface layer has been determined to be Cr2O3 by XPS and XRD. The dense and uniform Cr2O3 surface layers play an ideal role of tunnel barriers in the CrO2 powder compacts. (C) 2000 American Institute of Physics. [S0003-6951(00)00344-2].