A facile spray pyrolysis fabrication of Sm:CdS thin films for high-performance photodetector applications

https://doi.org/10.1016/j.sna.2020.111952Get rights and content

Highlights

  • Facile fabrication of Sm:CdS thin film photodetector was developed.

  • High responsivity of 1.01 AW−1 for Sm:CdS compare to pure (0.213 AW−1).

  • High specific photodetectivity was noted ∼ 2.21 × 1012 Jones for Sm:CdS.

  • Excellent photosensitivity of ∼ 4.9 × 103 compare to pure CdS (∼ 2.0 × 103).

  • Very high EQE of ∼257 % was observed for Sm:CdS compare to pure CdS.

Abstract

Achievement of high-performance photodetectors based on CdS is a key field of research and challenge in the current scenario. Here, facile fabrication and characterization of novel samarium (1, 3 and 5 wt.% Sm)-doped CdS thin films for the photodetector applications have been demonstrated. The fabricated films show good crystallinity with crystallites size ranging 18–30 nm. The morphology and homogeneity of Sm-doping ingrown films were confirmed through scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX). Field emission SEM study reveals the low dimension nanograins formation and the films are free from voids and cracks. The effects of Sm-doping on linear and nonlinear optical properties of the fabricated thin films have been elucidated. The optical parameters such as refractive index, energy gap, susceptibilities were noticed to be reduced by Sm-doping in CdS thin films. An emission peak around 536 ± 14 nm was observed in PL spectra of pure CdS which was found to be shifted and quenched by Sm-doping. Finally, the photodetector performance of the fabricated thin films has been investigated for 532 nm laser light. The photodetector based on the 1 wt.% Sm:CdS shows an improved performance (higher responsivity of 1.01 AW−1, higher detectivity of 2.21 × 1012 Jones, excellent photosensitivity of ∼4.9 × 103, and very high external quantum efficiency (EQE) of 257 %) compared to pure CdS (responsivity of 0.213 AW−1, detectivity of 7.43 × 1011 Jones, photosensitivity of ∼2.0 × 103, and EQE of 249.70 %). These results propose a much simpler route to achieve high-quality CdS films for photodetector applications.

Introduction

From photodetection application point of view, the search for advanced materials with exceptional characteristics is in high demand in recent scenario [[1], [2], [3], [4], [5], [6], [7], [8]]. The visible light photodetectors are noted to be considerably important in several usages like care of the environment, research-based on space, and optics-communications. Also, there is a massive demand for fast response devices which can increase the operating speed of the device. Cadmium sulfide (CdS) belongs to II–VI semiconductor group which is often exploited in optoelectronics owed to the widespread direct bandgap of ∼2.4 eV. CdS are highly attractive for several devices like opto-gas sensing, solar cell, owing to its noteworthy photosensitivity and quantum efficiency [[9], [10], [11], [12]]. It is reported that there is an increase in photocurrent of CdS by several orders underneath optimal radiance [13]. CdS is noticed to be of high interest from photodetectors applications point of view, and several researchers has been reported the photodetector characteristics of it in pure as well as doped form such as: Waldiya et al. reported the photodetection properties of CBD prepared CdS nanoparticles films and the responsivity (R) was observed between 0.05 to 0.38 A/W@420 nm [14], Husham et al., prepared the films of CdS by MWCBD and found the responsivity between 0.075 to 0.25 A/W @400 to 650 nm region [15], Munde et al., fabricated the thick CdS films by spray pyrolysis and investigated the photodetection characteristics [16], Najm et al. thermally fabricated the Ag:CdS films and studied the photodetection properties and documented R values between 0.05 to 0.43 A/W @ 200–1000 nm [17]. Several reports are available on the above-mentioned key properties of CdS prepared in different forms using diverse techniques [8,[18], [19], [20], [21], [22]]. In parallel to modify the key characteristics of CdS films by employing the different techniques, precursors, mediums, temperature etc. it is important to modify these using suitable dopants. CdS films have fabricated with several dopants by different methods [[23], [24], [25], [26], [27], [28]].

Previously the rare earth like: Terbium (Tb), Ytterbium (Yb), Praseodymium (Pr), Neodymium (Nd), Europium (Eu), etc. doped CdS films have been reported [13,[29], [30], [31], [32]]. Samarium (Sm) is noted to play a vital role in changing the key opto-electrical properties of several semiconductors such as cadmium oxide, titanium dioxide, zinc sulfide, zinc oxide, [[33], [34], [35], [36], [37]]. Very recently, Shkir et al. reported the spray pyrolysis fabricated Eu@CdS and Pr@CdS films with improved photodetection properties and suitable device responsivity were noticed [38,39]. Sm doped CdS nanostructures are also prepared and reported by several researchers [[40], [41], [42], [43]]. Recently 1, 2, 3, 4 and 5 at.% Sm doped CdS films have been fabricated by Yilmaz et al., using spray pyrolysis process and investigate the structure-opto-electrical properties [44]. This report shows a limited study on Sm:CdS films fabricated by keeping the substrate at 400 °C as no photodetectors were fabricated and studied. As per reports on CdS the several properties of it has been tremendously enhanced by changing the parameters/techniques of deposition/doping elements including photodetection performances.

Here, we fabricated thin films of CdS with 0, 1, 3, and 5 wt.% Sm doping using a spray pyrolysis process on a hot substrate at 310 °C and elaborating the detailed structural, vibrational, morphological, optical, photoluminescence, and nonlinear properties. Finally, the photodetector performance of the fabricated thin films has been investigated under the different illumination intensities of 532 nm laser light. The photodetector shows excellent performance with responsivity up to 1.01 AW−1, detectivity up to 2.21 × 1012 Jones, excellent Ion/Ioff ratio and a very high EQE up to 257 %.

Section snippets

Films preparation

We have bought cadmium Chloride (CdCl2), Thiourea (CS(NH2)2) and Samarium (III) acetate (Sm(O2C2H3)3. xH2O) of AR grade from Sigma Aldrich for depositing the CdS films on glass. Before depositing the films, the substrates of glass were washed several times and cleaned with acetone and dried with nitrogen flow. The solutions of CdS were prepared for spraying to fabricate the films by taking CdCl2 and Thiourea (1:2 ratio) in 10 ml solvent in 4 different bottles and mixed well by stirring at room

Structural and vibrational spectroscopic analyses

XRD patterns of grown Sm:CdS films are exhibited in Fig. 1, reveals the polycrystalline nature of the films with a single hexagonal phase with some new peaks of Sm2O3 owing to Sm doping in CdS. The XRD spectra contains major peaks corresponds to the following planes: (100), (002), (101), (102), (110), (103) and (112) are completely agreeing to standard data (JCPDS No. 041-1049) which shows a hexagonal phase of films. The additional peaks appear at 30 and 34.5° assigned to Sm2O3 [CIF@1530724].

Conclusions

In conclusions, Sm-doped CdS nanostructured thin films have been successfully fabricated using a facile spray pyrolysis technique for photodetectors application. The nature of the grown films was found to be crystalline and favorably grown along (002) direction. The XRD and the vibrational study confirms the formation of CdS nanocrystals as the spectra comprise all fundamental peaks. The surface morphology was captured through SEM/EDX and signify the formation of nanoscale grains and free from

Declaration of Competing Interest

Authors declare that there is no conflict of interest in the current work.

Acknowledgements

The authors would like to express their gratitude to the RCAMS at King Khalid University, Saudi Arabia for sanctioning grant (RCAMS/KKU/001-20). The authors also extend their sincere appreciation to the Deanship of Scientific Research at King Saud University, Riyadh for funding this work through Research Group No. (RG-1438-094).

Mohd. Shkir. He was born in Utter Pradesh, India in 1982. He received the B.Sc. and M.Sc. degree in Physics from M.J.P. Rohilkhand University, Bareilly, India. He received his Ph.D degree in Physics from Jamia Millia Islamia, New Delhi, India in 2011. He performed his Postdoc in the Crystal Growth Lab (CGL), Universidad Autónoma de Madrid, Madrid, Spain with Prof. E. Diegues. He has received many awards namely DS Kothari Post-Doctoral fellowship award, MNRE-SEC-Research Associate, ‘Award for

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    Mohd. Shkir. He was born in Utter Pradesh, India in 1982. He received the B.Sc. and M.Sc. degree in Physics from M.J.P. Rohilkhand University, Bareilly, India. He received his Ph.D degree in Physics from Jamia Millia Islamia, New Delhi, India in 2011. He performed his Postdoc in the Crystal Growth Lab (CGL), Universidad Autónoma de Madrid, Madrid, Spain with Prof. E. Diegues. He has received many awards namely DS Kothari Post-Doctoral fellowship award, MNRE-SEC-Research Associate, ‘Award for Revolutionary Findings’, IAAM Young Scientist Medal 2018, Singapore, etc. Currently he is serving as an Assistant Professor in Department of Physics at King Khalid University, Abha, Saudi Arabia since 2013. He has published over 270 research papers in high impact national and international journals with over 3864 citations, h-index-33, i10-index 130 and also got International patent on solar cell fabrication system [P201331206]. His area of research includes nano-synthesis of different kind of materials for biomedical, optoelectronic and radiation detection applications. He leads many research groups in past and currently leading a research group "Investigation On Novel Class Of Materials (INCM)" at KKU.

    I.M. Ashraf. He is an Associate Professor at the Department of Physics, King Khalid University, Abha, Saudi Arabia and full professor in Department of Physics, Aswan University, Egypt. He completed his Ph.D. from Asiut University, Egypt in 1994. He has published several articles in materials science specially in opto-electronics and crystal growth.

    Aslam Khan. He received the B.S. and M.S. degrees in Chemistry from Aligarh Muslim University, Aligarh, India. He received his Ph.D. degree in Materials Chemistry from Jamia Hamdard, New Delhi, India in 2003. He was with the Centre for Biomedical Engineering and Centre for Nanotechnology, Indian Institute of Technology, Delhi & Guwahati as a Scientific Officer, from 2003 to 2007. In 2007, he joined NanoPhotonics & NanoMedical research group (www.nanotrio.com), Pohang University of Science & Technology (POSTECH), South Korea as a Postdoctoral Fellow. In 2008, he joined King Abdullah Institute for Nanotechnology, King Saud University, Riyadh, Saudi Arabia, where he is currently working as an Assistant Professor and leading a research group of Biomedical Nanotechnology. He has published more than 70 research articles in reputed peer-reviewed International Journals. His current research interest includes colloids and interfaces science, metal nanoparticles, broad areas of nanoscale science and technology involving synthesis, reaction and assembling of nanoscale materials.

    Mohd Taukeer Khan is working as an Assistant Professor at the Department of Physics, Islamic University of Madinah, Saudi Arabia. His research is focused to understand the device physics of future optoelectronics devices in particular, organic solar cells and perovskites solar cells. He obtained his PhD degree in organic/inorganic hybrid solar cells from the National Physical Laboratory, New Delhi and University of Delhi, India. He was a postdoctoral researcher at The University of Leeds, U.K. in the field of organic spintronics.

    Ahmed Mohamed El-Toni. He received his undergraduate from faculty of science, Cairo University in 1996. Dr. El-Toni earned his PhD in 2006 from, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University (Japan) on the synthesis of core-shell nanoparticles as sun-screening materials. In 2007, he held a post-doctoral position at National Institute of Advanced Industrial Science and Technology (AIST), Nagoya (Japan) on Development of Honeycomb-type Micro Fuel Cells. In 2008 he joined King Abdullah Institute for Nanotechnology (KAIN), King Saud University. Currently, he holds Associate Professor position in KAIN. He has published more than 100 scientific papers so far in reputed journals. Dr. El-Toni had conducted research relevant to synthesis, characterization and functionalization of nanomaterials, especially core-shell nanomaterials (solid core-shell, solid core-porous shell, rattle core-shell, hollow spheres). His current research interests are the synthesis of novel core-shell multifunctional nanomaterials, mesoporous nanocomposites and their application to drug delivery, enzyme immobilization, catalysis and water treatment.

    Salem AlFaify. He has Ph.D degree in Condense Matter Physics & Nanomaterials in 2011 from Western Michigan University, USA. He is a Professor in the Department of Physics, King Khalid University, Abha, Saudi Arabia. He is a team leader of the Quantum Functional Materials for Advanced Applications (QFMAA) and a leading researcher at the Advanced Functional Materials and Optoelectronics Laboratory (AFMOL) at King Khalid University. He was a president of Saudi Physical Society (SPS). He has authored and co-authored more than 200 articles in peer-reviewed reputed journals. His research interest is primarily in the area of the condensed matter physics at the nano-scale, in particular, the correlation nature of the nano-quantum structures and their properties and applications

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