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.
Highlights
Amorphous semiconductors have been known for years, and a lot of work on the applications of these materials is available in the literature [1,2]
The material is typically vaporized into a lowdensity gas, and the vapors move from the hot source to the glass substrate, which is pasted at the top of the tube
On the basis of the best fitting of optical absorption data, it is suggested that the band gap follows direct optical transitions and its value decreases on adding the Se content to the presently studied system
Summary
Amorphous semiconductors have been known for years, and a lot of work on the applications of these materials is available in the literature [1,2]. Glassy selenium is one of the popular materials for the Tellurium-rich glassy alloys of Se-Te are widely used for commercial, scientific, and technological purposes Their application ranges from optical recording media to xerography [15,16,17]. We found that these nanorods are aligned and their structure is completely amorphous These amorphous nanorods show an enhanced and direct band gap as compared to the reported results on polycrystalline materials [19,20]. These findings in the field of nanochalcogenide glasses will be interesting for applications in devices as these materials are cost-effective, and fabricating devices using these materials will reduce the cost of devices. Keeping the above facts in view, it is extremely important to study the properties of as-prepared a-SexTe100−x aligned nanorods
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