Height Control of Metallic Nanoislands by Quantum Confinement

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We studied the nucleation of flat-top, nano Ag islands of a uniform height at clean Si(111)7x7 and H-terminated Si(111) surfaces. At these surfaces, Ag islands of atomically flat-top grow. In the Ag islands, the sp-band electrons are confined along surface normal direction, between the Ag island surface and Ag/Si interface to reveal quantum well states. In this study, we elucidated the relation between the height and the quantized electronic states of the confined electrons along surface normal direction using optical second harmonic generation (SHG) intensity oscillation and scanning tunneling microscope (STM)/ scanning tunneling spectroscopy (STS). We also calculated the quantum well states numerically by two-band model. The calculation agreed well with the experimental results.