Low activation energy for the crystallization of amorphous silicon nanoparticles

Abstract

We have experimentally determined the crystallization rate of plasma-produced amorphous silicon powder undergoing in-flight thermal annealing, and have found a significant reduction in the activation energy for crystallization compared to amorphous silicon thin films. This finding allows us to shed light onto the mechanism leading to the formation of high quality nanocrystals in non-thermal plasmas.

Crystallization of solution processable amorphous tetrabenzoporphyrin films

“…The crystal nucleation and growth process from amorphous phases have always been interesting topics for a range of materials from nanocrystalline metallic materials [21][22][23] to polycrystalline silicon films [24][25][26]. There are some fundamental differences between the inorganic and organic semiconductor materials during the re-crystallization process as the former involves breaking and forming strong valence bonds, like in the case of silicon [27], while the latter involves mostly weak Van der Waals force.…”

Hydrogen-plasma-induced Rapid, Low-Temperature Crystallization of μm-thick a-Si:H Films

“…Currently practical plasma deposition of microcrystalline silicon is technologically and commercially hindered by the difficulties in attaining high-growth-rate preparation of large-area films at low temperature3. Solid-phase crystallization (SPC)4567 of amorphous hydrogenated silicon (a-Si:H) is one of the important alternatives to acquire high-quality polycrystalline silicon. There have been many reports on the SPC-fabricated polycrystalline silicon already utilized in thin film transistor89 and thin film solar cells1011.…”

“…However, the commonly used SPC conducted in a furnace requires a high temperature (>600 °C) and a long-time (>10 h) thermal annealing because the formation of crystalline nuclei in the precursor a-Si matrix has to overcome a large barrier energy of ~5 eV1213. Thus, metal-induced crystallization (MIC)914, field-enhanced crystallization (FEC)151617 and plasma-induced crystallization (PIC)618 have been proposed, and their feasibilities have been evidenced by the effective lowering of the crystallization temperature and the reducing of the incubation time for the formation of crystalline nuclei. Compared with MIC and FEC, PIC is more convenient, requiring only the introduction of hydrogen plasma instead of a catalyst or an additional field.…”

“…Compared with MIC and FEC, PIC is more convenient, requiring only the introduction of hydrogen plasma instead of a catalyst or an additional field. A growing number of attempts have been made in hydrogen plasma-induced post-deposition crystallization of a-Si:H thin films4618. Hydrogen plasma treatment causes numerous complicated reactions such as hydrogen diffusion/insertion and annihilation of strained Si-Si bonds419.…”

The Interplay of Quantum Confinement and Hydrogenation in Amorphous Silicon Quantum Dots

“…NPs within bulk materials present very different characteristics compared to “free‐standing” NPs or QDs: these include fundamental differences (e.g., matrix‐induced mechanical strain, phonon interactions), different synthesis challenges (e.g., hydrogenation is challenging to control within a bulk matrix) and different application focus (e.g., not suitable for applications that require colloids). Free‐standing a‐Si NPs have been synthesized using vacuum/low‐pressure plasmas28, 29, 30 to verify, for instance, the intermediate stage leading to the formation of c‐Si NPs and the effect of quantum confinement and hydrogenation has not been so far addressed. Furthermore and importantly, in all the above studies the investigations have been limited to NPs with diameters greater than ≈4 nm, i.e., NPs that are too large to exhibit properties originating from the strong quantum confinement regime.…”