Structural and Photoconductivity Properties of Tellurium/PMMA Films

Abstract

(http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.Owing to the very brittle nature of tellurium powder, nanoscopic grains with an average size of 4.8 ± 0.8 nm were produced by dry vibration milling technique using a mixer/mill apparatus. A novel material was obtained by binding the nanosized tellurium grains with poly(methyl methacrylate) (PMMA) polymer. The morphology, elemental composition, and structural and optical properties of Te/PMMA films were investigated. The prepared material was composed of hexagonal tellurium and α-phase of tellurium oxide. The electrical properties of the films were studied, for different electrode contact configurations, in dark condition and under white light illumination varying the optical power density from 2 to 170 mW/cm2 and turning the light on and off cyclically. Data analysis shows that the photoconductivity of the film with sandwich contact configuration is a linear function of the light power density and increases more than 2 orders of magnitude as compared to the photoresponse of the film with coplanar contact configuration.Keywords: Tellurium; Vibration milling; Poly(methyl methacrylate); Photoconductivity BackgroundElemental tellurium is a p-type semiconductor that can be exploited for many technological applications in metallurgy, photovoltaics, photonics, electronics, and medicine [1]. It has been used in the form of thin films or powder to fabricate gas sensors [ 2,3], antiseptic materials [4], photoconductors [5][6][7], thermoelectric devices [8][9][10][11], etc.Usually, chemical and electrochemical methods ("bottom-up" approaches), such as chemical vapor deposition [12] and solvothermal synthesis [13], are utilized to produce tellurium-based materials. In particular, one-dimensional (1D) tellurium nanostructures such as wires, rods, tubes, and belts have been synthesized. For example, Rao et al. [14] reported controlled synthesis of Te nanorods, nanowires, nanobelts, and related structures by the disproportionation of NaHTe in different solvents, Xia et al. [15,16] In this paper, results on a top-down approach [24], based on dry vibration milling technology, to reduce the size of a brittle material such as tellurium and produce nanoscopic phases in a simple, effective, and inexpensive way, are reported. Indeed, nanostructures in the form of fine tellurium powder composed of grains with average size of a few nanometers were produced in air, without any temperature control and chemical reactions.Furthermore, a novel functional material was obtained as monolithic film by binding the tellurium nanopowders with poly(methyl methacrylate) (PMMA), an amorphous thermoplastic polymer widely used in spectroscopic and optoelectronic applications.Further advantages of this preparation method are the following: (i) the slight toxicity of tellurium is reduced by embedding it in the form of powder into a polymeric matrix thus overcoming the limits for an in...

Structural and dielectrical properties of PMMA/TiO2 composites in terms of free volume defects probed by positron annihilation lifetime spectroscopy

“…The particle size and homogeneous dispersion of the particle in the polymer matrix can also be related to peak intensities and peak areas. 25 In the 30 and 50 mg TiO 2 -added samples, the peak observed at 25° (d 101 plane of TiO 2 ) is sharp. Thus, it can be concluded that the filler grain size is low and the homogeneity is high in the 30 and 50 mg TiO 2 -added composites where severe peaks are observed compared to other composites.…”