Structural Changes as a Function of Thickness in [(SnSe) 1+δ ] m TiSe 2 Heterostructures
Structural Changes as a Function of Thickness in [(SnSe) 1+δ ] m TiSe 2 Heterostructures
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[(SnSe) 1 δ ] m TiSe 2 异质结构中的结构变化随厚度变化
DOI：
10.1021/acsnano.7b07506
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发表时间：
2018
期刊：
影响因子：
17.1
通讯作者：
Johnson, David C.
中科院分区：
文献类型：
--
作者：
Hamann, Danielle M.;Lygo, Alexander C.;Esters, Marco;Merrill, Devin R.;Ditto, Jeffrey;Sutherland, Duncan R.;Bauers, Sage R.;Johnson, David C.
由于结构变化和将维度从三维降低到二维的新兴电子特性，单层和多层金属硫属化物化合物引起了人们的极大兴趣。为了探索 SnSe 的维数效应，由设计的薄膜前驱体制备了一系列具有增加 SnSe 层厚度 (m= 1–4) 的 [(SnSe)1+δ]mTiSe2 共生结构。面内衍射图表明，SnSe 成分 asmis 的基面发生了显着的结构变化。他们= 1化合物的扫描透射电子显微镜横截面图像表明层之间的长程相干性，而他们≥ 2化合物显示组成层之间广泛的旋转无序。 Form≥ 2，SnSe 成分的图像包含 SnSe 双层的各种堆叠序列。密度泛函理论计算表明，几种不同的 SnSe 堆叠序列的形成能相似。这些化合物显示出意想不到的传输特性，因为mis增加，包括在(MSe)m(TiSe2)n化合物中观察到的第一个p型行为。其中≥2化合物的电阻率均大于form=1，其中m=2最大。在室温下，霍尔系数为正形式 = 1，负形式 = 2–4。它们= 2化合物的霍尔系数随着温度降低而改变符号。然而，室温塞贝克系数从负值转变为正值 atm= 3。这些特性与单带传输不相容，表明这些化合物不是简单的复合材料。
Single- and few-layer metal chalcogenide compounds are of significant interest due to structural changes and emergent electronic properties on reducing dimensionality from three to two dimensions. To explore dimensionality effects in SnSe, a series of [(SnSe)1+δ]mTiSe2intergrowth structures with increasing SnSe layer thickness (m= 1–4) were prepared from designed thin-film precursors. In-plane diffraction patterns indicated that significant structural changes occurred in the basal plane of the SnSe constituent asmis increased. Scanning transmission electron microscopy cross-sectional images of them= 1 compound indicate long-range coherence between layers, whereas them≥ 2 compounds show extensive rotational disorder between the constituent layers. Form≥ 2, the images of the SnSe constituent contain a variety of stacking sequences of SnSe bilayers. Density functional theory calculations suggest that the formation energy is similar for several different SnSe stacking sequences. The compounds show unexpected transport properties asmis increased, including the first p-type behavior observed in (MSe)m(TiSe2)ncompounds. The resistivity of them≥ 2 compounds is larger than form= 1, withm= 2 being the largest. At room temperature, the Hall coefficient is positive form= 1 and negative form= 2–4. The Hall coefficient of them= 2 compound changes sign as temperature is decreased. The room-temperature Seebeck coefficient, however, switches from negative to positive atm= 3. These properties are incompatible with single band transport indicating that the compounds are not simple composites.