Crystallization from amorphous structure to hexagonal quantum dots induced by an electron beam on CdTe thin films

• Published in: Journal of crystal growth 2009-02, Vol.311 (5), p.1245-1249
• Main Authors: Becerril, M., Zelaya-Angel, O., Medina-Torres, A.C., Aguilar-Hernández, J.R., Ramírez-Bon, R., Espinoza-Beltran, F.J.
• Format: Article
• Language: English
• Subjects: A1. Crystal morphology; A1. Nanostructures; A1. X-ray diffractions; B2. Semiconducting II–VI materials; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Materials science; Nanoscale materials and structures: fabrication and characterization; Other topics in nanoscale materials and structures; Physics; Quantum dots; Solid-solid transitions; Specific phase transitions
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2008.12.056

Amorphous cadmium–telluride films were prepared by rf sputtering on Corning 7059 glass substrates at room temperature. The deposition time was 10 and 12 h with a thickness of 400 and 480 (±40 nm), respectively. As-prepared films were amorphous according to X-ray diffraction (XRD) patterns, but a win-fit-software analysis of the main XRD broad band suggests a wurtzite structure at short range. Transmission electron microscopy (TEM) at 200 keV produces crystallization of the amorphous CdTe. The TEM-electron beam induces the formation of CdTe quantum dots with the wurtzite hexagonal structure (the metastable structure of CdTe) and with ∼6 nm of average grain size. As effect of a probable distortion of the CdTe crystalline lattice, the unit cell volume (UCV) shrinks to about 30% with respect to the bulk-UCV of CdTe. Besides, the energy band gap increases as expected, according to literature data on quantum confinement.