3D Imaging and Manipulation of Single Vacancy Defects

3D Imaging and Manipulation of Single Vacancy Defects

Scientific Achievement
(a) Charge rings around defects, from tip-induced band bending, identify the specific layer on which the defect resides; (b) After a tip pulse at 1.0 V, a new vacancy is created at a sublattice layer, labelled L2a; (c) Two vacancies are negatively charged at a tip bias of 0.9 V; (d) A vacancy at sublattice layer L2a becomes negatively charged at 0.7 V.  (hi-res image)

A scanning tunneling microscope (STM) tip is used to write and erase (move) individual vacancies on a crystalline lattice in multiple layers of PdSe2, and then to switch the charge state of the defect.

Significance and Impact

The ability to image and manipulate single vacancies enables creation of on-demand defects to control phases and quantum states for computing. 

Research Details

- An STM is used to reveal  and control Se vacancy defects in PdSe2.

- Above a threshold voltage, the tip creates and erases (moves) vacancies; below that threshold, the same tip can be used to change the charge state of the vacancy defect.

- First-principles calculations confirm a small diffusion barrier and reveal diffusion pathways of Se vacancies.


G. D. Nguyen, L. Liang, Q. Zou, M. Fu, A. D. Oyedele, B. G. Sumpter, Z. Liu, Z. Gai, K. Xiao, and A.-P. Li, "3D imaging and manipulation of subsurface selenium vacancies in PdSe2," Phys. Rev. Lett121, 086101 (2018).  DOI: 10.1103/PhysRevLett.121.086101

CNMS Researchers