Nanocrystalline Si thin films with arrayed void-column network deposited by high density plasma

Abstract

High porosity nanocrystalline Si thin films have been deposited using a high density plasma approach at temperatures as low as 100 °C. These films exhibit the same unique properties, such as visible luminescence and gas sensitivity, that are seen in electrochemically etched Si (i.e., porous Si). The nanostructure consists of an array of rodlike columns normal to the substrate surface situated in a void matrix. We have demonstrated that this structure is fully controllable and have varied the porosity up to ∼90% (as derived from optical reflectance) by varying the deposition conditions. In particular, the impact of plasma power has been found to reduce porosity by increasing the nuclei density and therefore the areal density of columns. Humidity sensors have been demonstrated based on the enhanced conductivity of our films (up to 6 orders of magnitude) in response to increase in relative humidity. Depending on the porosity, the conductivity-relative humidity behavior of our films shows variations which can be correlated with the nanostructure. Also, these variations indicate that the dominant charge transport is limited by the dissociation of water into its ions at the column surfaces.

Laser desorption/ionization mass spectrometry on nanostructured semiconductor substrates: DIOS™ and QuickMass™

“…The surface is continuous but has voids parallel to the surface. It was noted that the surface morphology of the QuickMass TM substrates, does not share a similarity with the columnar/voids Si thin-film substrate produced by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) described in [36][37][38]. According to the reference sources [39,40], the QuickMass TM substrate was prepared by physical vapor deposition (PVD) and this deposited thin-film replaced the columnar/voids film developed previously, because the columnar/voids film tended to have a high chemical background in the low mass region of the mass spectra, due to hydrocarbon contaminants adsorption.…”

Study on the initial growth process of crystalline silicon films on aluminum-coated polyethylene napthalate by Raman spectroscopy

“…And it is exciting that some successful models have been proposed to explain the formation process of crystalline silicon films: (1) surface diffusion model [8,9], (2) etching model [10] and (3) chemical annealing model [11]. Meanwhile, because of the light weight and flexibility demanded in modern solar cells and personal information displays, such as e-books, cellular phones, the preparation of high-quality crystalline silicon thin films on plastic has been attracting much attention the recent years [12][13][14][15]. And some approaches have been proposed to manufacture crystalline silicon on polymer substrates, such as laser annealing crystallization of amorphous silicon films [14,16] and the deposition of crystalline silicon films assisted with the appropriate substrate temperature, about 100 1C or more, in plasma chemical vapor deposition (CVD) processes [12,14,17,18].…”

“…Meanwhile, because of the light weight and flexibility demanded in modern solar cells and personal information displays, such as e-books, cellular phones, the preparation of high-quality crystalline silicon thin films on plastic has been attracting much attention the recent years [12][13][14][15]. And some approaches have been proposed to manufacture crystalline silicon on polymer substrates, such as laser annealing crystallization of amorphous silicon films [14,16] and the deposition of crystalline silicon films assisted with the appropriate substrate temperature, about 100 1C or more, in plasma chemical vapor deposition (CVD) processes [12,14,17,18]. However, some drawbacks in the above-mentioned approaches severely block the preparation of high-quality crystalline silicon films on plastic substrates.…”

Deposition and field emission properties of highly crystallized silicon films on aluminum-coated polyethylene napthalate

“…To date, two approaches are used to manufacture crystalline silicon films on plastic, i.e. laser annealing crystallization (LAC) of amorphous silicon films [6,8] and the deposition of crystalline silicon films assisted with the appropriate substrate temperature, about 100 1C or more, in plasma chemical vapor deposition (CVD) process [4,6,9,10]. However, some drawbacks in the above-mentioned approaches severely block the preparation of high-quality crystalline silicon films on plastic substrates.…”

“…They have been used in solar cells, thin film transistors, imaging sensors and large-area flat displays. Meanwhile, because of the light weight and flexibility demanded in modern personal information displays, such as e-books, cellular phones, the preparation of high-quality crystalline silicon thin films on plastic has been attracting much attention in these years [4][5][6][7]. To date, two approaches are used to manufacture crystalline silicon films on plastic, i.e.…”