Multi-band silicon quantum dots embedded in an amorphous matrix of silicon carbide

Abstract

Silicon quantum dots embedded in an amorphous matrix of silicon carbide were realized by a magnetron co-sputtering process and post-annealing. X-ray photoelectron spectroscopy, glancing x-ray diffraction, Raman spectroscopy and high-resolution transmission electron microscopy were used to characterize the chemical composition and the microstructural properties. The results show that the sizes and size distribution of silicon quantum dots can be tuned by changing the annealing atmosphere and the atom ratio of silicon and carbon in the matrix. A physicochemical mechanism is proposed to demonstrate this formation process. Photoluminescence measurements indicate a multi-band configuration due to the quantum confinement effect of silicon quantum dots with different sizes. The PL spectra are further widened as a result of the existence of amorphous silicon quantum dots. This multi-band configuration would be extremely advantageous in improving the photoelectric conversion efficiency of photovoltaic solar cells.

Comparative study of electroluminescence from annealed amorphous SiC single layer and amorphous Si/SiC multilayers

“…The formation of Si QDs in SiC single layer and in amorphous Si/SiC multilayers is a little different. For SiC single layer, the formation of Si QDs is accompanied by the formation of Si-C bonds during the annealing process [4,15], which can suppress the nucleation and the growth of Si QDs. However, for Si/SiC multilayers, the Si QDs are formed just in amorphous Si sublayers, so a large number of nucleation occurs.…”

“…Meanwhile, the bandgap of a-SiC can be easily modulated by controlling the film composition. Recently, several reports have been published on the fabrication and physical properties of Si QDs embedded in amorphous SiC matrix [3][4][5][6]. It was found that Si QDs can be formed by thermal annealing amorphous SiC films and the photoluminescence band was shifted by adjusting the Si QDs size due to quantum confinement effect (QCE) [7].…”

Electron tomography analysis of 3D interfacial nanostructures appearing in annealed Si rich SiC films

“…3,4 To understand the relationship between the absorber layer structure and optical properties, the size of the Si NPs was analyzed in SRSO films. [5][6][7][8] However, it has turned out that the interfacial properties of the Si NPs play a decisive role in determining the optical absorption and the optical activity of the Si NPs as concluded on both experimental and theoretical grounds. 9 From atom probe tomography (APT) of SRSO films, a very thin compositionally distinct interfacial layer was observed between the Si NPs and the surrounding matrix.…”

Impact of silicon quantum dot super lattice and quantum well structure as intermediate layer on p‐i‐n silicon solar cells

“…An electron inside a QD cannot move freely in all directions, so it behaves like an atom, which provides the opportunity to control the energy carrier states. With such QDs spaced sufficiently close together forming a quasi‐crystal structure, overlap of the wave functions of quantum‐confined carriers in adjacent dots enables the formation of a real QD super lattice (QDSL) with the confined states smearing out to form a miniband . Conventional molecular beam epitaxy technology, although well‐developed, can achieve only very limited control along the growth direction, which induces a mixture state from the wet layer.…”