Effect of hydrogen gas on the growth process of PbS nanorods grown by a CVD method Ramin Yousefi a, * , Mohsen Cheraghizade b , Farid Jamali-Sheini c , Wan Jefrey Basirun d , Nay Ming Huang e a Department of Physics, Masjed-Soleiman Branch, Islamic Azad University (I.A.U.), Masjed-Soleiman, Iran b Department of Electrical Engineering, Bushehr Branch, Islamic Azad University (I.A.U.), Bushehr, Iran c Department of Physics, Ahwaz Branch, Islamic Azad University, Ahwaz, Iran d Department of Chemistry, University of Malaya, and also Nanotechnology & Catalysis Research Centre, Institute of Postgraduate Studies, University of Malaya, 50603 Kuala Lumpur, Malaysia e Low Dimensional Materials Research Center, Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia article info Article history: Received 23 February 2014 Received in revised form 24 April 2014 Accepted 20 May 2014 Available online 29 May 2014 Keywords: PbS nanorods Chemical vapor deposition Sulfuration Optical properties abstract PbS nanostructures were grown by sulfuration of two lead sheets in a tube furnace under nitrogen (N 2 ) and argon/hydrogen (Ar/H 2 ) conditions. All conditions, such as the sheet temperature, sulfur powder temperature, and the carrier gas rate, were the same for two samples. Field emission scanning electron microscope (FESEM) images showed that the nanostructures with rod morphology were formed on the sheets. However, the nanorods that were grown under N 2 gas, were denser, more compact, and a different shape and size in comparison to another sample. In addition, the nanorods grown under N 2 gas exhibited a rectangular shape, while another sample showed nanorods that were tapered. X-ray diffraction (XRD) patterns indicated that these nanorods were PbS with a cubic phase. Furthermore, Raman measurements confirmed the XRD results, and indicated three Raman active modes of PbS phase. The optical characterization results showed a band gap for the PbS nanorods in the infrared region. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Metal chalcogenide semiconductors have considerable attracted much attention because of their potential for various applications. In fact, semiconducting metal chalcogenide nanocrystals (IIeVI and IVeVI) are a class of materials that exhibit band-gap energies, spanning from the mid-to-near infrared (PbS, PbSe, PbTe) to the visible (CdS, CdSe, CdTe), and into the ultraviolet (ZnS, ZnSe) region. Lead sulfide (PbS) is one of these semiconductors with a direct and narrow band gap of 0.41 eV at room temperature and a large exciton Bohr radius of 18 nm, which permits size-quantum confinement effects to be clearly visible, even for larger particles [1]. Therefore, it has important optical applications, such as solar cells and infrared detectors [2], solar control coatings [3], optical fibers, and broadband optical amplifiers [4]. In addition, from a technological perspective, PbS is an extremely promising material for a large number of applications in the mid- and near-infrared emission and detection range, biological applications, and optoelectronic devices, owing to its wide range of size-dependent properties [5]. So far, various forms of PbS nanostructures, such as nanowires [6], nanorods [7e9] and nanoclusters [10], have been reported, which were grown by various methods such as chemical bath deposition (CBD) [11], electrochemical deposition [6], hydro- thermal [12,13], and vacuum evaporation [14]. Most of these techniques are usually complex, expensive, and time-consuming. Based on these reasons, in this work we present a simple and cost-effective method to grow PbS nanorods on a large scale. A simple sulfuration of the lead sheets was used to grow PbS nano- rods in a chemical vapor deposition (CVD) set-up. In addition, we report and discuss the effect of hydrogen gas on morphology, structure, and optical properties of the PbS nanorods. 2. Experimental sections The PbS nanostructures were grown using the following proce- dure. Firstly, six high purity Pb sheets (99.99%), with dimensions of 2  1 cm and a thickness of 0.5 mm were used as substrates. The sheets were cleaned ultrasonically with acetone and methanol, for 10 min in each solvent. Then the sheets were put into a horizontal tube furnace * Corresponding author. Tel.: þ98 9166224993; fax: þ98 6813330093. E-mail addresses: Yousefi.ramin@gmail.com, raminyousefi@iaumis.ac.ir (R. Yousefi). Contents lists available at ScienceDirect Current Applied Physics journal homepage: www.elsevier.com/locate/cap http://dx.doi.org/10.1016/j.cap.2014.05.010 1567-1739/© 2014 Elsevier B.V. All rights reserved. Current Applied Physics 14 (2014) 1031e1035