SCANNING-PROBE-MICROSCOPY STUDIES OF SUPERLATTICE STRUCTURES AND DENSITY-WAVE STRUCTURES IN 2H-NBSE2, 2H-TASE2, AND 2H-TAS2 INDUCED BY FE DOPING
SCANNING-PROBE-MICROSCOPY STUDIES OF SUPERLATTICE STRUCTURES AND DENSITY-WAVE STRUCTURES IN 2H-NBSE2, 2H-TASE2, AND 2H-TAS2 INDUCED BY FE DOPING
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DOI：
10.1103/physrevb.48.14543
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发表时间：
1993-11-15
影响因子：
3.7
通讯作者：
COLEMAN, RV
中科院分区：
文献类型：
--
作者：
DAI, Z;XUE, Q;COLEMAN, RV
Fe嵌入到2 H相过渡金属二硫属化合物NbSe 2、TaSe 2和TaS 2的货车范德华能隙中产生了许多有趣的电子、磁性和结构效应。扫描隧道显微镜（STM）和原子力显微镜（AFM）被证明是非常敏感的这些变化，我们报告了广泛的结果作为铁浓度的函数。所有三种材料在低温下的纯态下都支持类似的3a 0 X 3a 0电荷密度波（CDW）结构。在低浓度的Fe的CDW超晶格仍然是强在4.2 K，并坚持高浓度的Fe。在高浓度下，Fe在货车德瓦耳斯能隙中的八面体空穴中变得有序，并观察到2a 0 × 2a 0和平方根3a 0 ×平方根3a 0的超晶格。在300 K和4.2 K下都可以检测到这些。4.2 K下的STM光谱显示，在2 H-FexNbSe 2和2 H-FexTaSe 2中，电子光谱中的能隙最初减小，但在较高的Fe浓度下稳定下来，并且对于有序的2a 0 X 2a 0相保持良好的定义。从CDW到混合CDW和自旋密度波状态的过渡被指示，因为这些高Fe浓度相是反铁磁性的。在~ 2 H-FexTaS_2中观察到2a 0 × 2a 0和平方根3a 0 ×平方根3a 0超晶格。2a 0 × 2a 0区域显示出大的能隙，而平方根3a 0 ×平方根3a 0则没有。后一相是铁磁性的，并且预期不会表现出间隙。在整个Fe浓度范围内的电子结构的发展已经被STM和AFM跟踪，并且可以详细跟踪。
The intercalation of Fe into the van der Waals gap in the 2H phase transition-metal dichalcogenides NbSe2, TaSe2, and TaS2 produces many interesting electronic, magnetic, and structural effects. The scanning tunneling microscope (STM) and atomic force microscope (AFM) prove to be very sensitive to these changes and we report a wide range of results as a function of Fe concentration. All three materials support similar 3a0 X 3a0 charge-density-wave (CDW) structures in the pure state at low temperatures. At low concentrations of Fe the CDW superlattice is still strong at 4.2 K and persists to high concentrations of Fe. At high concentrations, the Fe becomes ordered in the octahedral holes in the van der Waals gaps, and superlattices of the form 2a0 X 2a0 and square-root 3a0 X square-root 3a0 are observed. These can be detected at both 300 and 4.2 K. STM spectroscopy at 4.2 K shows that in 2H-FexNbSe2 and 2H-FexTaSe2 the energy gap in the electronic spectrum is initially reduced, but stabilizes at higher Fe concentrations and remains well defined for the ordered 2a0 X 2a0 phase. A transition from a CDW to a mixed CDW and spin-density-wave state is indicated, since these high Fe concentration phases are antiferromagnetic. In 2H-FexTaS2 both 2a0 X 2a0 and square-root 3a0 X square-root 3a0 superlattices are observed. The 2a0 X 2a0 regions show a large energy gap, while the square-root 3a0 X square-root 3a0 do not. The latter phase is ferromagnetic and would not be expected to exhibit a gap. The development of the electronic structures over the entire range of Fe concentrations has been followed by STM and AFM and can be tracked in detail.