Fabrication and Measurement of Arrays of Few-Donor Quantum Dots

NIST is using atomically precise fabrication to develop electronic devices for use in quantum information processing and quantum materials research. We are using hydrogen-based scanning probe lithography (STM) to enable deterministic placement of individual dopant atoms with atomically aligned contacts and gates to fabricate single and few atom transistors, as well as coupled few donor/quantum dot devices for spin and charge readout.

Here, we extend the STM-patterning method to fabricate coupled arrays of few atom clusters having multiple donors per dot, including a functional 3×3 quantum dot array device. Using the Si(100)2x1 surface reconstruction lattices as a natural atomic ruler, we designed the separation between a dot and its nearest neighbor dots or source/drain leads to span the regime from weakly coupled to strongly coupled ~ 5 to 8 nm separation. Low-temperature transport measurements are used to investigate the electron levels and energy spectra formed in individual dots versus energy spectra across the array of dots that result from the hybridization of quantum states. Combining electrical measurement results with simulations, we analyze the tunnel and capacitance couplings within this device to explore the rich physics in dot-arrays.