Sixth Sense Lab - Research

Research

Projects

Ongoing Sponsored Projects:

DST National Quantum Mission (NQM) Project on Quantum Sensing and Metrology (Role: Member PI under QMet Hub, IITB TG)
ISRO (RESPOND) project on Design and Development of Oven-controlled MEMS Resonator (Role: PI)
DST (TDP-AMT) project on Single step process for photomask fabrication (Role: PI)
ICMR project on Development of micro RNA-based electrochemical biosensor for early detection of non-small cell lung cancer (Role: Co-PI)

Completed Sponsored Projects:

SERB (CRG) project on Investigating the Photophysics, Chiroptics and Electron Transport Properties of Helical Tautomeric Scaffolds (Role: Co-PI)
SERB (SRG) project on Development of a scanning probe tool for micro and nanoscale patterning. (Role: PI)
SERB (CVD) project on AI-enabled Modular Robust Reliable and Efficient Multi-flow Oxygen Concentrator (Role: Co-PI)

Focused Research Areas

Nano-patterning and Lithography

Electrolithography: Electric current, assisted by Joule heating, can induce long-range flow of material in thin film of Cr (APL 104, 214102, 2014; IEEE TED 60, 2877, 2013). Using this electromigration driven material flow on thin chromium film we invented a new, versatile, scanning probe based lithography technique named as electrolithography. In electrolithography, we perform electromigration induced selective metal etching with the help of a conducting scanning probe, and then transfer the patterns to other materials using a polymer layer (PMMA). Electrolithography does not require UHV condition, high-power e-beam source or UV sources like conventional lithography techniques. We have achieved pattern resolutions of 9 nm on the polymer and 40 nm on transferring the pattern to another material. In electrolithography, any polymer and corresponding developer can be used thereby, removing need of costly and toxic chemicals. Electrolithography can be used for drawing patterns having dimensions from a few nanometres to a few hundred micrometres.
Constructive Lithography: In constructive lithography, patterns are drawn on a highly ordered organosilane monolayer (OTS), self-assembled on silicon, using localized chemical reaction induced by an electrically biased tip or a focused e-beam. The basic principle of this patterning technique is based on a water bridge-mediated electrochemical oxidation process to selectively convert surface exposed top −CH3 groups of the monolayer to −COOH. Using this patterning technique, macro, micro and nano surface channels having exciting electronic properties have been successfully fabricated with resolution up to 20 nm.Ref: J. Berson et al., Nat. Mater. 14, 613-621, 2015

Material Transport

Electromigration in conducting thin films is a major reliability issue associated with microelectronics circuits. In case of solid metals, the net electromigration force, as shown in the figure, pushes atoms from the cathode to the anode, resulting in formation of void(s) near cathode and material pile-up in the vicinity of the anode. This creates an open circuit at the cathode and hillocks or whiskers at the anode that may cause short-circuit. On the other hand, in the case of liquid electromigration, the material first melts due to Joule heating and then the liquefied material starts to flow in a directional fashion as long as the electric current flows through it. The direction of flow or material transport in the case of liquid electromigration depends on the material: for liquid Au, Al, Ga, Sn, In, etc., the flow occurs from the anode to the cathode (i.e., in the direction of the electric field), whereas in the case of liquid Pb, etc., the liquefied material flows in the opposite direction of the applied electric field. Unlike the slow mass transfer under the conventional solid-state electromigration resulting in “void and protrusion” formation after an extended period of time, the mass transfer due to the liquid electromigration is extremely rapid. Therefore, liquid electromigration also poses severe reliability concern in the microelectronic systems comprising very thin films carrying currents of large current densities.

Sensing Applications

Cantilever beams, membranes, etc., based deflecting and vibrating structures are at the center of the micro- and nano -sensors. Sensed stimuli, such as force, rotation, gas concentrations, etc., induce deflection in those beam or membrane elements, directly or indirectly, and the desired parameters can be calculated from the measurement of the deflection. This deflection can be measured optically (in AFM), electrically (change in resistance and capacitance), or by some other means. Electric field driven material transport can induce percolation network in the microstructure of a material. The electrical resistance of this percolated microstructure is very sensitive to generated strain or applied force. Single layer nanochannels of –COOH group patterned on Si surface should also be very sensitive to stress and strain. A little amount of strain can induce large change in resistance which will be useful in force sensors.

System Development

Our lab also focuses on design, integration and automation of systems for various applications. The systems are being developed as cost-effective alternatives to commercially available systems.

µ-ELG: A table-top prototype system is being developed for performing Lithography at ambient condition. We need to interface a 3-axis mocro/ nano positioners, electrical source measurement unit, a force sensor, high resolution optical system, and an electronic display board with the master computer using feedback controlled algorithm. In this system different hardware components need to be linked using two Arduino microcontroller boards (Atmega and UNO) and software part will be taken care of using LABVIEW (NI).

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