Optical and structural properties of amorphous Se x Te100-x aligned nanorods

Abstract

In the present work, we report studies on optical and structural phenomenon in as-deposited thin films composed of aligned nanorods of amorphous SexTe100-x (x = 3, 6, 9, and 12). In structural studies, field emission scanning electron microscopic (FESEM) images suggest that these thin films contain high yield of aligned nanorods. These nanorods show a completely amorphous nature, which is verified by X-ray diffraction patterns of these thin films. Optical studies include the measurement of spectral dependence of absorption, reflection, and transmission of these thin films, respectively. On the basis of optical absorption data, a direct optical band gap is observed. This observation of a direct optical band gap in these nanorods is interesting as chalcogenides normally show an indirect band gap, and due to this reason, these materials could not become very popular for semiconducting devices. Therefore, this is an important report and will open up new directions for the application of these materials in semiconducting devices. The value of this optical band gap is found to decrease with the increase in selenium (Se) concentration. The reflection and absorption data are employed to estimate the values of optical constants (extinction coefficient (k) and refractive index (n)). From the spectral dependence of these optical constants, it is found that the values of refractive index (n) increase, whereas the values of extinction coefficient (k) decrease with the increase in photon energy. The real and imaginary parts of dielectric constants calculated with the values of extinction coefficient (k) and refractive index (n), are found to vary with photon energy and dopant concentration.

Influence of annealing temperature on the structural and optical properties of As30Te70 thin films

“…For the films under investigation, the best fit for the dependence of (αhν) 1/r versus hν was obtained when r = 1/2. Thus, the allowed direct transition process is involved for the as-prepared and annealed As 30 Te 70 thin film which is in an agreement with the results reported in previous studies [31,32].…”

A DFT study of SenTenclusters

“…The HL gap of the investigated geometries concurs with the optical band gap of the amorphous Se (1− x ) Te x system. 26,67 Furthermore, our values of the HL gap, Table 1 , are close to the reported energy gap of a-Se, 1.99 eV, and higher than that of a-Te, 0.5 eV. 37 …”

“…HOMO-LUMO gap determine the optical properties of a material. HL gap of the inves-tigated geometries concur with optical band gap of amorphous Se (1−x) T e x system [26,67].…”

“…Presence of small structures or defects in thin films has significant impact on their structural and functional properties [24,25]. Synthesis, characterization and different properties of Se − T e nanostructured thin films [26,27] have been reported in literature. Amorphous nano structured Se − T e films have shown enhanced and direct band gap not reported for their counterparts [28,29], crystals.…”

Untitled

“…3). The creation of EHPs as a result of exciton dissociation occurs at the interface between the perovskite and the charge transport layer 25 . The produced charge carriers are subsequently delivered to their appropriate electrodes via the solar cell's transporting layers.…”