Evaluation of the potential distribution in a multiple stacked Si quantum dots structure by hard X-ray photoelectron spectroscopy

Abstract

Six-fold stacked Si quantum dots (Si-QDs) structures with ultrathin SiO2 interlayers were formed on ultrathin SiO2 layer/n-Si substrates by low-pressure chemical vapor deposition using a SiH4 gas and their vertical electric potential distributions were evaluated using hard X-ray photoelectron spectroscopy under a DC bias application to the semitransparent electrodes formed on the stacked Si-QDs structure. The Si1s photoelectron spectra due to Si–Si bonding units can be deconvoluted into seven components corresponding to the six Si-QDs layers and Si substrate. Obviously, the energy shift between the components for two adjacent dots layers becomes larger towards the upper side of the stacked dots structure. This result indicates that the electric field concentrates on the upper side and is consistent with the proposed model that can explain the ballistic electron emission characteristics from multiple stacked Si-QDs structures.

Semiconductor Quantum Dots as Target Analytes: Properties, Surface Chemistry and Detection

“…Hence, surface analysis techniques are of high interest, and X-ray photoelectron spectroscopy (XPS) is deserving of particular mention. In fact, the literature shows that XPS has been the technique of choice for the analysis of the surface of a variety of QDs [ 8 , 171 , 172 , 173 , 174 , 175 , 176 , 177 ], although as previously mentioned, authors often combine XPS and other techniques with characterization purposes.…”

“…Finally, XPS is not only useful for investigating “simple” QDs but also much more complex structures, such as the 6-fold stack of Si QDs layers embedded in an ultrathin SiO 2 matrix. This material was prepared by Futamura et al [ 176 ], who investigated the electron emission mechanism when the structure was subjected to DC biases, concluding that electrons gain kinetic energy mainly in the upper side of the stacked Si QDs structure.…”

Electron Field Emission from Multiply-Stacked Si Quantum Dots Structures with Graphene Top-Electrode

“…In our previous work, we succeeded in the fabrication of multiple-stacked Siquantum-dots (Si-QDs) layers with ultrathin SiO2 interlayers by repeating low-pressure chemical vapor deposition (LPCVD) using pure SiH4 and dry O2 thermal oxidation (12)(13). Recently, we also demonstrated electron emission from diodes with multiple-stacked Si-QDs structures under biases of 6V and over, in which electric field is concentrated the upper dot layers as evaluated by hard X-ray photoelectron spectroscopy (14)(15)(16)(17)(18)(19). To enhance electron emission efficiency, one major issue regarding the electron emission device application of the multiple-stacked Si-QDs is minimizing electron scattering at top electrodes.…”