D.Banerjee Research Group

» Temperature variation DC and AC electrical characterization 

We measure temperature dependent dc and ac properties of organic bulk heterojunction and reduced graphene oxide (RGO) based composites in temperature range of 85K-473K. For temperature dependent measurements, the samples were mounted in a liquid nitrogen cooled dipstick cryostat filled with small amount of He exchange gas. The cryostat is kept evacuated at a vacuum pressure of 5×10-6 mbar during the measurements. Temperature was controlled using a home-made temperature controller built around an industrial PID unit (Honeywell 1010). The controller offers temperature stability of ±0.5K throughout the whole range.

AC properties may be measured with out arsenal of lock-in amplifiers (LIA) and LCR meters. Measurements under DC bias and AC frequency range of 10 mHz to 4 MHz is possible. We have access to department's HP-Agilent impedance analyzer 4291a.

» Electrical characterization under illumination 

We investigate temperature dependent (85K-460K) photoresponse and carrier mobility of reduced graphene oxide (RGO) and RGO based composites under illumination by using a bath type optical cryostat. For these measurements current-voltage (J-V) characteristics are recorded by using Keithley 2450 source measure unit. The samples are illuminated with a Xenon lamp through a quartz window. The sample chamber is kept at 5×10-6 mbar vacuum pressure during measurements. Temperature stability is ±0.5K throughout the whole temperature range.

» CVD Furnace

 We are working on thin film deposition using liquid precursor to undergo degradation at the desired temperature to form a thin film on the substrate at elevated temperature. Therefore we have designed a high temperature tube furnace (~1400°C) with Silicon carbide heating element along with mass flow controller (MFC with flow range between 0 to 100 SCCM). The tube furnace is a controlled atmosphere type fitted with a two stage rotary vacuum pump for deposition of non-oxide compounds. This furnace can be used as for the vapour phase deposition of many liquid precursors along with pyrolysis of various films. Therefore it can be used for both depositions as well as curing according to our requirement. It is a cost effective supplement for the high priced chemical vapour deposition unit.

 » Thermal evaporation cum DC sputtering unit. (Manufactured by: Indian High Vacuum Pump)

Made by Indian High Vacuum Pumps. Aluminium, Silver, and Cupper contacts can be deposited by this system. Depositions are carried out under high vacuum condition which is obtained by a Rotary pump (pressure ∼ 10-3 mbar) and a Diffusion Pump (pressure ∼ 10-6 mbar). Uniform and smooth Al & Ag contacts can be done by thermal evaporation. DC magneto sputtering unit enables to get uniform cupper deposits by ion sputtering in presence of Argon plasma.

 » Wet lab facilities--

                 • Glove Box (Customise by us) : A custom made glove box enables us to deal with different chemical processes safely

                  • Spin coater :

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 centre of the substrate. The substrate is then rotated at high speed in order to spread the coating material by centrifugal force. A machine used for spin coating is called a spin coater, or simply spinner. 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. 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. In our lab, we have an Apex instruments made spinNXG-P1 spin coater with the following  features-

       a) Very High Speed Range: 100 -10,000 Rotations per minute

       b) Very High Acceleration: 40- 5,000 Rotations per minute

       c) High Duration Range: 1- 9,999 seconds per step

       d) Less than 1 percent error across full speed range

       e) N2 purging facility

                   • Autoclave : 

A custom made stainless steel autoclave of 100 ml with Teflon lining is used for chemical reaction and other processes at an elevated temperature.         

                  • Hot air oven : 

In our lab we have three custom made hot air oven, enabling us to cure/anneal our samples in a temperature range from 300 to 2500 C with fan facility. 

                    • Centrifuge :

A centrifuge is an instrument that spins an object around a fixed axis with a very high speed, thus enabling to separation of higher dense particles from lower  ones. In our lab, we have a RM-12C centrifuge made by REMI with the following   features-

    a) Max speed: 16,000 r.p.m.

    b) Max capacity: 24 ml.

    c) Countdown timer range: 0-15 minutes.

                   • 650 W Probe Sonicator:

A probe sonicator is a versatile tool that uses ultrasonic cavitation in liquids for various applications. It can be employed to break down different types of cells, bacteria, viruses, and both animal and plant tissues. Additionally, it is used for emulsification and separation, homogenization, extraction, defoaming, cleaning, nanomaterial preparation, dispersion, and to speed up chemical reactions. This instrument is widely utilized in fields such as biology, medicine, agriculture, chemistry, materials science, pharmaceuticals, and other areas of education, research, and production. 

                   • Cryostat Bath System:

A cryostat bath is an apparatus designed to keep a constant low temperature for scientific and industrial purposes. It includes a chamber containing a cooling fluid, such as liquid nitrogen or helium, maintained at a low temperature. Cryostat baths are commonly utilized in laboratories for experiments that need stable and precise temperature regulation. 

» Microwave Plasma Cleaner:

Plasma cleaning systems are versatile tools used for various surface cleaning applications prior to processing. They are effective at removing surface oxidation and eliminating mineral residues from surfaces. 

»  DAQ6510 Data Acquisition / Multimeter System:

The DAQ6510 Data Acquisition and Logging Multimeter System features an intuitive touchscreen that simplifies configuration with its visual and user-friendly test setups. It offers real-time visualizations of scan status, helping to quickly identify issues and prevent lost testing time, and facilitates easy analysis of test data. 

»  Wire Bonder:

It is used to interconnect microelectronic components such as semiconductor devices, chips, LEDs, and PCBs by welding metal wires to bonding pads using ultrasonic energy, pressure, and temperature. In our lab we have HB02 wire bonder which is capable of both Ball/Wedge and Wedge/Wedge bonding with a simple tool change. It features a user-friendly TFT display for easy operation and quick adjustment of bond parameters. 

»  Four probe sample stage:

The four probe sample stage is customized by us to measure the resistivity and conductivity of the delicate samples.

»  Lock-in Amplifier:

A lock-in amplifier is an electronic instrument designed to measure the amplitude and phase of small AC signals, even when there is a lot of noise present. It is especially useful for isolating signals with a specific frequency from a noisy background.

»  LCR Meter:

IM 3536 LCR meters provide a broad range of testing frequencies, from DC and 4 Hz to 8 MHz, with an accuracy of 0.05%. This makes them ideal for assessing the characteristics of next-generation electronic components, such as power supply inductors, due to the instrument's maximum measurement frequency of 8 MHz.

»  Broadband light sources:

A broadband light source is a device that emits light over a wide range of wavelengths or frequencies, covering a broad spectrum. Unlike narrowband sources, which emit light within a limited range of wavelengths, broadband sources provide a more continuous and extensive range of wavelengths. This makes them useful for applications that require a wide spectrum of light, such as spectroscopy, color matching, and illumination for various types of sensors and imaging systems. In our lab we have two type of broadband light source:

                   • Xenon lamp : 

A Xenon Arc lamps provide a strong and steady source of continuous light. The intense light produced from the short arc between the anode and cathode makes these lamps highly effective as point sources. They can be precisely focused using the right lens setup or directed onto a fiber bundle for re-imaging.          

                   • Quartz Halogen lamp: 

Quartz Halogen lamps are preferred for radiometric and photometric applications, as well as for providing excitation sources of visible to near-infrared (NIR) light.