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.