Research Projects

In situ heating of materials and devises in Scanning Electron Microscope (SEM) provides valuable insights into real time structural and morphological changes as a function of temperature. Compared to conventional in situ heaters, Micro-Electro-Mechanical Systems (MEMS) based in situ heaters provide confined heating, better temperature control, uniformity of heating and faster heating rates. However, high material cost, complex fabrication methods and the lack of reusability adds to the operating cost of the metal-based MEMS heaters. This necessitates the identification of alternate materials for the heating coils, affordable fabrication methods and development of reusable MEMS based heating systems. All carbon microheater which are fabricated through laser graphitization can be a cost effective and easy to fabricate alternative for conventional metal based microheaters. Laser graphitization involves exposing a polymer to a focused laser beam, where the extreme heat induces localized heating, resulting in the graphitization of the material. The resulting carbon structures are ideal for applications requiring high-performance microheaters. However, temperature stability of the polymer limits the use of these heater to lower temperature. The polymer surrounding the carbon coil can degenerate at high temperature, with evolution of volatile gasses degrading the vacuum. The present study proposes a two-step graphitization process, in first step, a carbon microheater is fabricated on the polymer which is fixed on top of a suitable substrate. In the second step, the polymer surrounding the carbonized microheater is removed by higher laser power, producing an all carbon microheater. This will increase the temperature stability of the heater and eliminates the degradation of the polymer making it suitable for high temperature inert operations. Moreover, to ensure the reuse of the MEMS heating systems, a design is proposed where the sample is placed in a removable thin membrane placed on top of the heating coil. The proposed all carbon microheater and the reusability of the microheater can considerably reduce the cost of the in situ heating systems and will make it more accessible to the research community.