Cryogen-free scanning gate microscope for the characterization of Si/Si_0.7Ge_0.3 quantum devices at milli-Kelvin temperatures

The conduction band of bulk Si exhibits a six-fold valley degeneracy, which may adversely impact the performance of silicon quantum devices [1]. The spatial characterization of valley states in Si remains limited; especially in functional quantum devices. We describe here a cryogen-free scanning gate microscope for the characterization of Si/Si_0.7Ge_0.3 quantum devices at mK temperatures. The microscope is based on the Pan-walker design, with coarse positioning piezo stacks and a fine scanning piezo tube [2]. To reduce the pulse tube noise, we utilize both active and passive vibration isolation mechanisms, and achieve a root-mean-square noise in z of ∼ 2 nm [3]. As a proof of concept, we use the microscope to manipulate the charge occupation of a Si quantum dot, opening up a range of possibilities for the exploration of quantum devices and materials

[1] Zwanenburg et al., Rev. Mod. Phys. 85, 961 (2013)

[2] Pan et al., Rev. Sci. Instrum. 70, 1459 (1999)

[3] Pelliccione et al., Rev. Sci. Instrum. 84, 033703 (2013)