Pribusová Slušná Lenka, Vojteková Tatiana, Hrdá Jana, Pálková Helena, Siffalovic Peter, Sojková Michaela, Végsö Karol, Hutár Peter, Dobročka Edmund, Varga Marián, Hulman Martin
Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, 84104 Bratislava, Slovakia.
Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 84536 Bratislava, Slovakia.
ACS Omega. 2021 Dec 14;6(51):35398-35403. doi: 10.1021/acsomega.1c04768. eCollection 2021 Dec 28.
Thin films of transition-metal dichalcogenides are potential materials for optoelectronic applications. However, the application of these materials in practice requires knowledge of their fundamental optical properties. Many existing methods determine optical constants using predefined models. Here, a different approach was used. We determine the sheet conductance and absorption coefficient of few-layer PtSe in the infrared and UV-vis ranges without recourse to any particular model for the optical constants. PtSe samples with a thickness of about 3-4 layers were prepared by selenization of 0.5 nm thick platinum films on sapphire substrates at different temperatures. Differential reflectance was extracted from transmittance and reflectance measurements from the front and back of the sample. The film thickness, limited to a few atomic layers, allowed a thin-film approximation to calculate the optical conductance and absorption coefficient. The former has a very different energy dependence in the infrared, near-infrared, and visible ranges. The absorption coefficient exhibits a strong power-law dependence on energy with an exponent larger than three in the mid-infrared and near-infrared regions. We have not observed any evidence for a band gap in PtSe thin layers down to an energy of 0.4 eV from our optical measurements.
过渡金属二硫属化物薄膜是用于光电子应用的潜在材料。然而，这些材料在实际应用中需要了解其基本光学性质。许多现有方法使用预定义模型来确定光学常数。在此，采用了一种不同的方法。我们在不依赖任何特定光学常数模型的情况下，测定了几层PtSe在红外和紫外-可见范围内的薄层电导率和吸收系数。通过在不同温度下对蓝宝石衬底上0.5nm厚的铂膜进行硒化处理，制备了厚度约为3-4层的PtSe样品。从样品前后表面的透射率和反射率测量中提取差分反射率。限于几个原子层的薄膜厚度允许采用薄膜近似法来计算光学电导率和吸收系数。前者在红外、近红外和可见光范围内具有非常不同的能量依赖性。在中红外和近红外区域，吸收系数对能量呈现出强烈的幂律依赖性，指数大于3。从我们的光学测量中，我们没有观察到任何证据表明PtSe薄层在能量低至0.4eV时存在带隙。
