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V K Jain, Speaker at Green Chemistry Conferences
Amity University, India
Title : Fabrication of heterojunctions on silicon nanowires on Si chip, CdS/p-Si for electricity generation from moisture and n-SnO2/p-Si for UV detection

Abstract:

Making a heterojunction on silicon nanowire (Si NW) on silicon chip is a promising candidate for preparing many new devices by doing band gap engineering. One-dimensional heterojunction devices are gaining attention because of improved carrier collection which results in improving the overall efficiency of a device. Herein, we report the synthesis of CdS/p-Si nanowires (NWs) hetero-junction device by wet-chemical methods and their potential application for electricity generation from atmospheric moisture. A single CdS/p-Si NWs hetero-junction based moisture enabled electricity generator (MEG) device exhibits a saturated maximum output voltage in the range of 250-300 mV and a saturation current of ~0.2 µA in presence of humid conditions. This primitive module acts as a promising candidate for future energy generation devices constituting of individual units connected either through simple series or parallel connection to scale up high electrical power. Generally, UV-sensors are made of silicon carbide, which require high processing time and costs. Herein, we have fabricated and characterized the ultrafast, very sensitive and selective UV sensor using silicon nanowires on silicon chip. The Metal Assisted Chemical Etching of poly-crystalline (pc) - p-Si has resulted into vertically aligned, uniform grown highly dense pc-SiNWs. These NWs on pc-p-Si substrate are decorated by SnO2 particles by using Electro-deposition technique. The prepared SiNWs/n-SnO2 heterojunction show diode like behaviour under UV-light exposure and shows significantly high rectification ratio, sensitivity, responsivity and detectivity around 172.3 at ±9 V, 64, 0.3456 A/W at 5 V and 8.02869 x 1012 Jones, respectively. The barrier height calculations suggest that the proposed Si NWs decorated with other desired metal oxides, the selective and sensitivity of the prepared heterojunction can be tuned for other required applications such as: IR and terahertz (THz) sensing.

Audience Take Away: 

  • This gives a method for making a new type of heterojunction and can tailor the barrier height according to requirement.
  • To understand the new science when it is in the nanowire form
  • It simplifies to use material like silicon instead of taking more complicated material. For example, for making silicon carbide for making UV detector, even silicon nanowires can be used.

Biography:

Dr. Jain has done his Ph.D. in Solid State Physics from IIT Delhi and was head of the silicon devices and Micro Electro Mechanical Systems (MEMS) division and developed many new technologies. His result of electro-luminescence in porous silicon was considered as the first International observation. He has published more than 200 papers in National & International journals, edited a few books and has filed more than 60 patents. He has received the Technology award in 2002. He has made a multidisciplinary department with most modern facilities in Amity University. He got the Award in 2012 from “Power of Ideas” (DST programme) and from Royal Academy of U.K. He has develop many technologies and some have been transferred to industries. He is working in the areas of photovoltaics, solar energy, thermal heat storage system, sensors, bio sensors, water purification, MEMS, lots of devices have been made using heterojunction Silicon nanowires and surface metallic plasmonic, etc.

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