Indium Nanowires and Nanodots Grown on In/Si(111) Surface
M. Xu, A. Okada, S. Yoshida, K. Kanazawa, K. Hayashi, O. Takeuchi and H. Shigekawa
Institute of Applied Physics, University of Tsukuba

Introduction:

Adsorption sites favorable for In adatoms on In-(4 × 1)

Low-dimensional nanostructures, like nanodots and nanowires, have been
extensively studied due to their unusual physical properties (metal to insulatortransition, quantum effects, and …) and potential applications in nanoelectronics(nanoscale electrodes, interconnections, single electron transistor, and …).

In atom of In-(4 × 1) chains

In adatom

Si atom of Si chains

Carbon nanotube transistor(Courtesy of Cees Dekker, Delft Institute of Technology, the Netherlands)

In-(4 × 1)

Favorable sites for In adatoms

Possible model structure of In nanowire
In atom of In nanowires

Charge density wave
in quasi-one-dimensional chains on Si(111)-In (4 × 1)[1]Nanowires and nanodots on Si surfaces are of particular interest not only for
their compatibility with Si-based device integration also for the possibility to be
used as model systems to explore phase transition and interesting quantum effects.
In/Si(111) surface is used as a substrate for the growth of In nanowires andnanodots.

-1V

3 nm

+ 0.6 V

3 nm

Nucleation and growth of In wires enhanced bystep (Enrlich-Schwoebel) barrier

Experimental:

No observation of In wire on
homogeneous In-(4 × 1)

Experiments were carried out in
UNISOKU UHV LT-STM system(P ≤ 1.5×10-8 Pa, T ≤ 10 K ).
Clean Si(111) surface was obtained
after outgassing at ~600 °C followed
by slowly heating to 850~900 °C andquickly flashing above 1200 °C. Aresistant-heating evaporator is used todeposit In with a flux of 0.4~6 ML
per min.

In - (4 × 1)

Si(111) substrate
LT-STM
Chamber

In adatom diffusion barrier
In wirePreparationchamber

In - (4 × 1)
In − ( 31 × 31 )In − ( 31 × 31 )Si(111) substrate

Shape transformation of In nanodots during annealing

Results and discussion:
Si(111) - In (4 × 1) and ( 31 × 31 ) surface

31 × 31

4 ×1

30 nm

In nanodots as grown

7.5 nm45 nm

Flat In islands after annealing

Conclusion and outlook:
150 nm15 nm

STM images of Inhomogeneous In/Si(111) surface

In - (4 × 1) and ( 31 × 31 )[1,2,3]

1) In nanowires and nanodots on In/Si(111) surface
 In nanowires and nanodots are grown on In-(4 × 1) andIn nanowires and nanodots on In/Si(111) surface

31 × 31surfaces, respectively.

 The formation of In nanowires is attributed to the anisotropic diffusion barriers caused by thestructural anisotropy of In-(4 × 1) substrate.
 A possible model structure is presented for In nanowires.
 In nanodots transform into flat In islands during annealing.

2) Research plan for coming experiments
 Electron confinement by In nanowires and nanodots
 Phase transition in In nanowires
References:

30 nm

3 nm

9 nm

Large-area STM image

Nanowires on In - (4 × 1)

N anodots on In - ( 31 × 31 )[1] H. W. Yeom, S. Takeda, E. Rotenberg, I. Matsuda, K. Horikoshi, J. Schaefer, C. M. Lee, S. D. Kevan, T. Ohta,T. Nagao, and S. Hasegawa, Phys. Rev. Lett. 82, 4898 (1999).
[2] O. Bunk, G. Falkenberg, J. H. Zeysing, L. Lottermoser, R. L. Johnson, M. Nielsen, F. Berg-Rasmussen, J. Baker,and R. Feidenhans'l, Phys. Rev. B 59, 12 228 (1999).
[3] A. A. Saranin, A. V. Zotov, A. N. Tovpik, M. A. Cherevik, E. N. Chukurov, V. G. Lifshits, M. Katayama,
and K. Oura, Surf. Sci. 450, 34 (2000).