Contents lists available at ScienceDirect Materials Science & Engineering B journal homepage: www.elsevier.com/locate/mseb Raman spectroscopy study of the wurtzite-zinc blende phase transition of bare CdSe nanoparticles J.A. Rivera-Marquez a , J.I. Contreras-Rascón b , R. Lozada-Morales c , J. Díaz-Reyes d, ⁎ , R. Castillo-Palomera b , M.E. Alvarez e , M. Meléndez-Lira f , O. Zelaya-Angel g a Facultad de Ingeniería Química, Benemérita Universidad Autónoma de Puebla, Av. San Claudio y 18 Sur, CU, Col. San Manuel, Puebla, Puebla 72590, Mexico b Posgrado en Energía Renovable, Ingeniería en Energía, Universidad Politécnica de Chiapas, Km 21.5 de la Carretera Tuxtla-Villaflores, Suchiapa, Chiapas 29150, Mexico c Facultad de Ciencias Fisicomatemáticas, Benemérita Universidad Autónoma de Puebla, Av. San Claudio y 18 Sur, CU, Col. San Manuel, Puebla, Puebla 72590, Mexico d Centro de Investigación en Biotecnología Aplicada, Instituto Politécnico Nacional, Ex-Hacienda de San Juan Molino, Km 1.5 de la Carretera Estatal Santa Ines Tecuexcomac-Tepetitla, Tepetitla, Tlaxcala 90700, Mexico e Posgrado en Nanotecnología, Departamento de Física, Universidad de Sonora, Rosales y Blvd, Luis Encinas, Col. Centro, Hermosillo, Sonora 83000, Mexico f Departamento de Física, CINVESTAV-IPN, Apdo. Postal 14-740, Ciudad de México 07000, Mexico g División de Investigación y Posgrado, Facultad de Ingeniería, Universidad Autónoma de Querétaro (UAQ), Centro Universitario, Querétaro, Qro. 76010, Mexico ARTICLE INFO Keywords: Chemical bath synthesis CdSe, nanoparticles Optical absorbance Raman spectroscopy ABSTRACT Structural and electronic properties characterization results show that the crystallographic structure of CdSe films, deposited by chemical bath synthesis, is controlled by the bath growth temperature. The synthesis parameters employed produced a set of nanostructured CdSe films on glass substrates with controlled crystal structure. The effect of bath temperature (T b ) on CdSe films was studied in the 0 ≤ T b ≤ 80 °C range. The average crystal diameter (AD) of the films lies within the 7 ≤ AD ≤ 12 nm interval, where AD depends on the selected T b . X-ray diffractograms (XRD) shown that at low T b values the formation of the hexagonal wurtzite (WZ) is promoted while at the other extreme the cubic zinc-blende (ZB) crystalline structure dominates. It is observed that the WZ → ZB transition occurs at the critical temperature T bc ~ 40 °C. The AD in each films for CdSe-NP’s was obtained from XRD analysis employing the Scherrer-Debye formula. The values of the lattice interplanar spacing (IS), determined from XRD analysis, as function of T b increases continuously except at temperatures around T bc where a local minimum is observed . The presence of stress acting on CdSe NP’s is identified by correlating the IS values with the crystalline structure: compression occurs for 0 ≤ T b ≤ 40 °C, and tension for 50 ≤ T b ≤ 80 °C. The band gap energy, obtained from optical absorption spectra, decreases monotonically but a local minimum is observed at T bc = 40 °C. Results from Raman spectroscopy show that the CdSe Raman LO-mode hardens for T bc as consequence of the WZ ↔ ZB structural transition. 1. Introduction Research on materials has been always an important activity of scientists because of the increasing demand of industrial progresses. At present, many works on new materials and structures are reported in topic like optoelectronics, solar cells, detectors, sensors, photocatalysts, among others [1–6]. Cadmium selenide (CdSe) is a II-VI compound with current good prospects for fabrication of advanced devices for varied applications [7]. CdSe is semiconductor with a direct band gap energy and may grow with both WZ or ZB crystallographic structure. It is important to have a methodology to control crystalline structure and tools to clearly iden- tify it. Photovoltaic devices production is a very important application of both bulk-CdSe and nanostructured material [1,2]. CdSe properties have been successfully applied in the production of single electron transistor, optoelectronics and flexible electronics [3–5]. Diverse ap- plications of CdSe NPs are reported in fields such as biological imaging [6], food industry [7], X-ray detectors [8], chemical detectors [9], photocatalysts [10], digital memories [11], etc. Nanostructured CdSe has been widely studied, the acquired knowledge has set the basis to explain the behavior of many properties of other nanostructured ma- terials [12]. The crystalline phase transformation from hexagonal wurtzite (WZ) to cubic zinc blende (ZB), and from WZ to rock salt (RS) happens in several semiconductor materials. The ZB ↔ RS transfor- mation in CdSe nanoparticles was reported by Tolbert and Alivisatos [13] establishing the basis for the understanding of this change of https://doi.org/10.1016/j.mseb.2020.114621 Received 5 February 2020; Received in revised form 7 June 2020; Accepted 4 July 2020 ⁎ Corresponding author. E-mail address: jdiazre@ipn.mx (J. Díaz-Reyes). Materials Science & Engineering B 260 (2020) 114621 0921-5107/ © 2020 Elsevier B.V. All rights reserved. T