Grant: Discovery Grants Program - Individual

Scanning probe microscopes (SPMs) have been extraordinarily effective tools for elucidating properties inherent to the nano-scale. Further development and application of SPMs is central to our overall research program. Our proposed studies will gain further fundamental understanding of surface-confined nano-scale properties of silicon. Concepts like field controlled computing, FCC, a basis for extremely fast and low power classical computing have been transformed by our discovery that silicon dangling bonds (DBs), created by removal of single H atoms from an H-terminated silicon surface, serve as atomic silicon quantum dots. Previous implementations required extreme cryogenic conditions. Coupled DBs make FCC viable at room temperature. The subject of coupled DBs is in its infancy. As pioneers of the concept and due to our facilities, substantial re-tooling, and previous work and collaborations, we are ideally positioned to explore it. Our newly established and highly stable 4 Kelvin SPM (both scanning tunneling microscope, STM, and atomic force microscope, AFM) allows us to enter a new fabrication and measurement regime. An integral field ion microscope allows routine deployment of our nitrogen stabilized single atom tip as a scanned probe. A second 4 K instrument, with magnet, and radio frequency detection capabilities will soon be operational, allowing most ideal ever single spin electron spin resonance measurements. The spectroscopy of single and coupled DBs will inform classical and quantum computing studies. Coulomb blockading effects will become accessible. AFM force scans will provide a new perspective on charge distributions at DBs. Extraordinary new AFM sensors we have developed enhance our chances of success. Experimental study of inter-DB tunneling through current-voltage, IV, spectra, with close coupled models developed with collaborators, will yield strength of interaction (~100 meV at 2 nm separation is expected) critically informing models of information conveyance by DB ensembles. Knowledge of DB coupling strength will guide an extensive joint theoretical and experimental program with Barry Sanders at Calgary that will assess tunnel rate and coherence properties. We predict ~10e5 coherent oscillations may be completed before a decohering event. In collaboration with Hong Guo at McGill, and with a co-supervised student, we will extend our joint studies of surface state mediated transport. We aim to reveal the nature and magnitude of such surface transport channels, thereby settling some controversy, and furthermore expect to indicate the possibility of connecting future nano-devices in this unique way. Our home made multi-probe STM will enable these atom-scale transport studies. DB-based wires, tunnel gaps and single electron transistors of unprecedented uniformity will be explored. With Konrad Walus of UBC, who works with dWAVE, the maker of a quantum annealing computer, we have a unique program of study for FCC circuit optimization.Woven throughout the proposal are refinements and applications of our nano-tips. The tip is fabricated by a chemical and field assisted, spatially restricted etch that leaves all but the apex W atom nitride coated. Unlike coating-free sharp metal tips, ours are extremely robust. A coherent electron emission opening angle of >14 degrees has been achieved, compared to ~3 degrees for any previous source. We calculate that 0.2 nm holographic projection microscope resolution is now possible, compared to 1.5 nm previously. High resolution and low beam damage will allow biological molecules to be imaged. Phase change around nano-magnets will be accessible. Our training record is excellent. Our students will get and will create jobs directly related to this work.