Thin Films

Title: Fabrication and Characterization of Polymer Nano Composites for MEMS application (in collaboration with Dept. ECE, NMIT)

Objective: To develop a composite material, which can be used to fabricate a voice detector and vibration sensor.

Title: All Oxide Solar Cells:

Objective: To develop a low cost solar cell with non toxic and abundant materials.

Description: Metal oxide (MO) semiconductors are promising for photovoltaic applications; many MOs are abundant, non-toxic and chemically stable. Today MOs are already widely used as active or passive components in a broad range of available commercial applications such as active channel layer in transistors that constitute the active matrix of displays or in solar cells as transparent conducting front electrodes and as electron or hole transport layers. Heterojunctions entirely based on MOs, so called all-oxide photovoltaic cells, are recently attracting considerable attention due to their promising potential for price reduction using cheap materials and production methods. As a p-type semiconducting oxide that can absorb visible light, cuprous oxide (Cu2O) is an attractive material for solar energy conversion. This material is gaining interest in photovoltaics field as a low cost material.

Title: Title: Growth of 2D materials like MoSe2 and WSe2 for microelectronic and optoelectronic applications

Objective: To develop ultra thin optoelectronic devices like light detectors (photo detectors) and transistors (2D transistors)


Infrastructure/Facilities

The area of thin films is a topic that is continuously gaining research attention, both for fundamental research point of view and for potential industrial applications. Broadly these thin films deposition techniques can be classified vapor deposition (CVD) techniques.

PVD technique available for thin film deposition in the nanomaterials and MEMS laboratory

The laboratory is equipped with sputtering-cum-activated thermal evaporation unit, where in one can use the same chamber for deposition of thin films in sputtering and thermal evaporation techniques, depending on the requirement. The picture and the schematic of the thin film coating unit is shown below.

The chamber is of 290 mm diameter and 350 mm height is mounted on a base plate provided with suitable feed through for electrical connections. The vacuum chamber can be evacuated to a base pressure of 1.0 X 10-6 diffusion pump+ rotary pump combination. Two Pirani gauges are connected to a Pirani-Penning gauge meter STA 6P4M utilized to measure the pressure in the vacuum chamber from 1000 mbar to 10-6mbar. A high power glow discharge facilitates the cleaning of the substrate surfaces prior to the deposition in order to achieve good adhesion of the film onto the substrate. mbar with the help of a conventional three state water cooled oil

Required substrate temperatures can be achieved by means of 1 KW radiant heater fixed above the substrate holder. The substrate temperature is controlled by a Eurotherm temperature controller (model 815 S).

For the sputtering process, the system is equipped with a magnetron source cathode (3” dia.) to achieve high density of plasma. It is equipped with a DC power supply with a current rating of 1 A at 2000 V.

CVD technique available for thin film deposition in the nanomaterials and MEMS laboratory

Here he volatile compound is made to decompose thermally and made to react with other gases, vapors or liquids to yield non-volatile reaction products on the substrate surface. The unit is equipped with a gas mixer which can mix two gases in required proportions.

Non-vacuum based thin film deposition unit

Spin coating is a procedure used to deposit uniform thin films to flat substrates. Usually a small amount of coating material is applied on the center of the substrate, which is either spinning at low speed or not spinning at all. The substrate is then rotated at high speed in order to spread the coating material by centrifugal force. Rotation is continued while the fluid spins off the edges of the substrate, until the desired thickness of the film is achieved. The applied solvent is usually volatile, and simultaneously evaporates. So, the higher the angular speed of spinning, the thinner the film. The thickness of the film also depends on the viscosity and concentration of the solution and the solvent.



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