Department of Chemistry, Physics and Atmospheric Sciences, Jackson State University, Jackson, MS 39217, USA.
Nanoscale. 2019 Oct 10;11(39):18449-18463. doi: 10.1039/c9nr04598h.
Black phosphorus (b-P) is an allotrope of phosphorus whose properties have attracted great attention. In contrast to other 2D compounds, or pristine b-P, the properties of b-P alloys have yet to be explored. In this report, we present a detailed study on the Raman spectra and on the temperature dependence of the electrical transport properties of As-doped black phosphorus (b-AsP) for an As fraction x = 0.25. The observed complex Raman spectra were interpreted with the support of Density Functional Theory (DFT) calculations since each original mode splits in three due to P-P, P-As, and As-As bonds. Field-effect transistors (FET) fabricated from few-layered b-AsP exfoliated onto Si/SiO2 substrates exhibit hole-doped like conduction with a room temperature ON/OFF current ratio of ∼103 and an intrinsic field-effect mobility approaching ∼300 cm2 V-1 s-1 at 300 K which increases up to 600 cm2 V-1 s-1 at 100 K when measured via a 4-terminal method. Remarkably, these values are comparable to, or higher, than those initially reported for pristine b-P, indicating that this level of As doping is not detrimental to its transport properties. The ON to OFF current ratio is observed to increase up to 105 at 4 K. At high gate voltages b-AsP displays metallic behavior with the resistivity decreasing with decreasing temperature and saturating below T ∼100 K, indicating a gate-induced insulator to metal transition. Similarly to pristine b-P, its transport properties reveal a high anisotropy between armchair (AC) and zig-zag (ZZ) directions. Electronic band structure computed through periodic dispersion-corrected hybrid Density Functional Theory (DFT) indicate close proximity between the Fermi level and the top of the valence band(s) thus explaining its hole doped character. Our study shows that b-AsP has potential for optoelectronics applications that benefit from its anisotropic character and the ability to tune its band gap as a function of the number of layers and As content.
黑磷（b-P）是磷的一种同素异形体，其性质引起了广泛关注。与其他二维化合物或原始的 b-P 相比，b-P 合金的性质尚未得到探索。在本报告中，我们对掺砷黑磷（b-AsP）的拉曼光谱和温度依赖的电输运性质进行了详细研究，其中 As 分数 x = 0.25。由于 P-P、P-As 和 As-As 键的存在，每个原始模式分裂为三个，因此用密度泛函理论（DFT）计算的支持来解释观察到的复杂拉曼光谱。在 Si/SiO2 衬底上剥离的少层 b-AsP 制成的场效应晶体管（FET）表现出空穴掺杂型传导，在室温下的 ON/OFF 电流比约为 103，在 300 K 时固有场效应迁移率接近约 300 cm2 V-1 s-1，当通过 4 端方法测量时，在 100 K 时增加到 600 cm2 V-1 s-1。值得注意的是，这些值与原始 b-P 的初始报告值相当或更高，表明这种水平的掺杂对其输运性质没有不利影响。在 4 K 时，ON 到 OFF 的电流比增加到 105。在高栅极电压下，b-AsP 显示出金属行为，电阻率随温度降低而降低，并在 T ∼100 K 以下饱和，表明栅极诱导的绝缘到金属转变。与原始 b-P 类似，其输运性质在扶手椅（AC）和锯齿形（ZZ）方向之间表现出很高的各向异性。通过周期性修正的杂化密度泛函理论（DFT）计算的电子能带结构表明费米能级与价带（s）顶部非常接近，从而解释了其空穴掺杂特性。我们的研究表明，b-AsP 具有潜在的光电应用前景，其各向异性特征和作为层数和 As 含量函数调谐其带隙的能力使其受益。
