Nano-engineered diamond tip chips for advanced imaging and data analysis applications in reverse-tip-sample scanning probe microscopy

The data quality in scanning probe microscopy (SPM) is directly linked to the quality of the SPM tip being used. The use of blunt, irregularly shaped, or multiple-contact points tips introduces convolution artifacts that compromise the measurement accuracy, not only in basic imaging but also in the quantitative assessment of material stiffness, surface adhesion, frictional force, electrical conductivity, etc. As a result, maintaining high data fidelity necessitates frequent tip exchanges which are time consuming, taking anywhere from ten minutes to several hours, depending on the instrument, operational mode, and experimental environment. Therefore, extensive research efforts have been done and recently converged on several innovative solutions, among which reverse tip sample (RTS) SPM developed at imec has emerged as a particularly promising approach.

In RTS SPM, the sample is placed on a tipless cantilever and is scanned over a tip integrated into the RTS probe chip, which contains thousands of such tips. This configuration allows for tip exchanges within mere seconds, a dramatic improvement compared to traditional SPM, simply by repositioning the sample above any adjacent, unused tip. In just a few years, the RTS technology has advanced rapidly and several RTS probe chip prototypes tailored for different applications have been demonstrated. These include chips equipped with bare silicon tips for topographical mapping, platinum coated tips for electrical SPM, and two robust, conductive diamond tip variants designed for high force and electrical measurements: conductive diamond coated silicon tips and sharp hedgehog full diamond tips (HFDTs).

The central objective of this project is to further improve the existing fabrication process and to establish robust protocols for precise control over the final diamond tip shape, thereby ensuring not only consistently sharp diamond tips but also enabling tailored geometries. A particular focus is on thin-film diamond growth and diamond dry etching. Complementing these efforts, the project also seeks to implement rigorous and efficient characterization methods for all tips, facilitating rapid feedback cycles for continuous fabrication process development. For this topic, the student will work inside imec’s state-of-the-art cleanroom environment to carry out the fabrication process using lithography, etching and deposition steps, and will do the tip performance evaluation in a well-equipped SPM lab. Finally, the student will summarize the project results in a publication.