4 research outputs found
Scanning-probe spectroscopy of semiconductor donor molecules
Semiconductor devices continue to press into the nanoscale regime, and new
applications have emerged for which the quantum properties of dopant atoms act
as the functional part of the device, underscoring the necessity to probe the
quantum structure of small numbers of dopant atoms in semiconductors[1-3].
Although dopant properties are well-understood with respect to bulk
semiconductors, new questions arise in nanosystems. For example, the quantum
energy levels of dopants will be affected by the proximity of nanometer-scale
electrodes. Moreover, because shallow donors and acceptors are analogous to
hydrogen atoms, experiments on small numbers of dopants have the potential to
be a testing ground for fundamental questions of atomic and molecular physics,
such as the maximum negative ionization of a molecule with a given number of
positive ions[4,5]. Electron tunneling spectroscopy through isolated dopants
has been observed in transport studies[6,7]. In addition, Geim and coworkers
identified resonances due to two closely spaced donors, effectively forming
donor molecules[8]. Here we present capacitance spectroscopy measurements of
silicon donors in a gallium-arsenide heterostructure using a scanning probe
technique[9,10]. In contrast to the work of Geim et al., our data show
discernible peaks attributed to successive electrons entering the molecules.
Hence this work represents the first addition spectrum measurement of dopant
molecules. More generally, to the best of our knowledge, this study is the
first example of single-electron capacitance spectroscopy performed directly
with a scanning probe tip[9].Comment: In press, Nature Physics. Original manuscript posted here; 16 pages,
3 figures, 5 supplementary figure
Gate-induced quantum-confinement transition of a single dopant atom in a silicon FinFET
The ability to build structures with atomic precision is one of the defining features of nanotechnology. Achieving true atomic- level functionality, however, requires the ability to control the wavefunctions of individual atoms. Here, we investigate an approach that could enable just that. By collecting and analysing transport spectra of a single donor atom in the channel of a silicon FinFET, we present experimental evidence for the emergence of a new type of hybrid molecule system. Our experiments and simulations suggest that the transistor\u27s gate potential can be used to control the degree of hybridization of a single electron donor state between the nuclear potential of its donor atom and a nearby quantum well. Moreover, our theoretical analysis enables us to determine the species of donor (arsenic) implanted into each device as well as the degree of confinement imposed by the gate