Research Description

Ph.D. Thesis: Investigation on Ge and axial Ge-TiO2 nanostructure synthesized using glancing angle deposition technique for photodetector application 

My  Ph.D. research work focused on the fabrication of low-dimensional metal/metal-oxide-semiconductor materials-based nanostructures for potential photodetector applications wherein Germanium (Ge) – thin-film (TF) and nanowire (NW) and coaxial titanium dioxide nanowire/germanium nanowire (TiO2-NW/Ge-NW) heterostructure were fabricated using the glancing angle deposition (GLAD) technique which is incorporated in an electron-beam (EB) evaporator coating system. GLAD is a simple and catalyst-free technique.

This technique extends the oblique angle deposition (OAD) technique. Germanium (Ge) is becoming more popular as a material for future electronics, primarily because of the high charge carrier mobility compared to silicon (Si) and other III-V semiconductors, which is in line with the International Technology Roadmap for Semiconductor (ITRS) recommendation for future technology. The structural characterization of germanium nanowires (Ge-NW) revealed the successful synthesis of vertical nanowires (NWs), which are polycrystalline in nature. An important observation was the detection of native germanium dioxide (GeO2 ) in the proposed nanostructures due to unintentional oxidation in ambient environmental conditions. The optical characterization revealed enhanced absorption in the germanium nanowire (Ge-NW) sample compared to the germanium thin-film (Ge-TF) sample. The electrical characterization of the germanium nanowire (Ge-NW) device exhibited superior photodetection performance compared to the germanium thin-film (Ge-TF) device.

Furthermore, germanium dioxide (GeO2) was passivated by incorporating titanium dioxide (TiO2) in the form of a coaxial titanium dioxide nanowire/germanium nanowire (TiO2-NW/Ge-NW) heterostructure. The structural characterization revealed the detection of both anatase and rutile phase titanium dioxide  (TiO2) at room temperature. The coaxial titanium dioxide nanowire/germanium nanowire (TiO2-NW/Ge-NW) heterostructure was synthesized to make further photodetector performance improvements compared to the pristine germanium nanowire (Ge-NW)-based photodetector. The structural, optical, and electrical parameter analyses were performed to investigate and validate the potential for photodetector application. In order to further understand the interface quality of the heterostructure, capacitance, and conductance analyses were performed, with the coaxial titanium dioxide nanowire/germanium nanowire (TiO2-NW/Ge-NW) device outperforming the germanium nanowire (Ge-NW) device. Furthermore, the electrical characterization of the coaxial TiO2-NW/Ge-NW heterostructure device showed an interface state density (Dit) of 3.3 × 108 eV-1cm-2  at 1 MHz and superior photodetection performance compared to the Ge-NW device. Finally, a broadband photodetector spanning from ultraviolet to near-infrared was achieved in the coaxial titanium dioxide nanowire/germanium nanowire (TiO2-NW/Ge-NW) heterostructure device, paving the way for future optoelectronics applications.

In conclusion, the coaxial TiO2-NW/Ge-NW heterostructure showed enhanced photodetection performance due to the reduction of Dit, which enhanced the charge carrier mobility while decreasing the defect trap density to improve the reliability and performance of the device.

List of Publications

Journals:

1. H Manas Singh, Ying Ying Lim and P Chinnamuthu, Electrical and dielectric parameters in TiO2-NW/Ge-NW heterostructure MOS device synthesized by glancing angle deposition technique, Scientific Reports, Vol. No. 11, pp. 19837, October, 2021

2. H Manas Singh and P Chinnamuthu, Investigation on the effect of interface state density and series resistance in Ag/Ge-NW/Si (MS) device synthesized by glancing angle deposition technique, Materials Letters, Vol. No. 300, pp. 130183, October, 2021

3. H Manas Singh, Bijit Choudhuri and P Chinnamuthu, Reduction of interface state density in coaxial TiO2/Ge nanowire assembly-based heterostructure and superior photodetector, Journal of Alloys and Compounds, Vol. No. 853, pp. 157344, February 2021

4. H Manas Singh, Bijit Choudhuri and P Chinnamuthu, Investigation of optoelectronic properties in germanium nanowire integrated silicon substrate using kelvin probe force microscopy, IEEE Transactions on Nanotechnology, Vol. No. 19, pp. 628- 634, July, 2020

Book chapter:

1.  P Chinnamuthu, P Pooja and H Manas Singh, “Synthesis of Nanowire Using Glancing Angle Deposition and Their Applications”, Nanowires-Recent Progress, edited by Xihong Peng. London: IntechOpen, 2020

Conference proceedings:

1. H Manas Singh and P Chinnamuthu, “The electrical parameters in Ag/Ge-NW/Si (MS) device as a function of frequency and voltage”, ICONN 2021 - 6th International Conference of Nanoscience and Nanotechnology, SRM IST, February, 2021

2. H Manas Singh and L S Singh, “FPGA based real-time underground mine environment monitoring and warning system”, RTEICT 2017 – 2nd IEEE International Conference on Recent Trends in Electronics, Information & Communication Technology, pp. 1084-1088, May, 2017