Aerosol assisted atmospheric pressure chemical vapor deposition of silicon thin films using liquid cyclic hydrosilanes

Abstract

Silicon (Si) thin films were produced using an aerosol assisted atmospheric pressure chemical vapor deposition technique with liquid hydrosilane precursors cyclopentasilane (CPS, Si 5 H 10) and cyclohexasilane (CHS, Si 6 H 12). Thin films were deposited at temperatures between 300-500 °C, with maximum observed deposition rates of 55 and 47 nm/s for CPS and CHS, respectively, at 500 °C. Atomic force microscopic analysis of the films depicts smooth surfaces with roughness of 4-8 nm. Raman spectroscopic analysis indicates that the Si films deposited at 300 °C and 350 °C consist of a hydrogenated amorphous Si (a-Si:H) phase while the films deposited at 400, 450, and 500 °C are comprised predominantly of a hydrogenated nanocrystalline Si (nc-Si:H) phase. The wide optical bandgaps of 2-2.28 eV for films deposited at 350-400 °C and 1.7-1.8 eV for those deposited at 450-500 °C support the Raman data and depict a transition from a-Si:H to nc-Si:H. Films possessing the highest photosensitivity of 10 2-10 3 under AM 1.5G illumination. Based on the growth model developed for other silanes, we present a possible mechanism that governs the film growth using CPS and CHS.

Syntheses and Molecular Structures of Liquid Pyrophoric Hydridosilanes

“…The differences in the packing indices of cyclopentane and cyclopentasilane (10) are not so big with values of 68.6 and 70.1 % respectively, but also present. The crystal structure of cyclopentasilane has been published before, [38] therefore we abstain from a detailed discussion of this structure.…”

“…The higher homologues of these compounds are seldom used, since they are difficult to handle and pyrophoric. However, the chemistry of hydridosilanes has received a considerable revival in recent years due to their potential use as precursors for liquid phase deposition of silicon films . This approach promises significant reduction of processing costs in the manufacture of semiconductor devices .…”

Toward the Mechanism of Perchlorinated Cyclopentasilane (Si5Cl10) Ring Flattening in the [Si5Cl10·2Cl]2– Dianion

“…[1][2][3][4][5][6][7][8][9][10][11] For CHS, the attraction to its practical applications is complemented by the interest generated in the structural and bonding features of its precursor, the complex dianion, [Si 6 Cl 12 ·2Cl] 2-, which consists of a planar Si 6 ring (in contrast to neutral Si 6 Cl 12 possessing D 3h symmetry [12][13] ) with two µ 6 coordinated chloride ions forming the apical vertices of a hexagonal bipyramid.…”

Approaching Solar‐Grade a‐Si:H for Photovoltaic Applications via Atmospheric Pressure CVD Using a Trisilane‐Derived Liquid Precursor

“…Intrinsic and doped inks have previously been synthesized from a variety of different monomers, these include the cyclic silanes cyclopentasilane (CPS, Si 5 H 10 ) and cyclohexasilane (CHS, Si 6 H 12 ), and the branched molecule neopentasilane (NPS, Si 5 H 12 ) . Solution‐processed a‐Si:H layers have been deposition via inkjet printing, spin coating, slot die coating, atmospheric pressure chemical vapor deposition (APCVD), and aerosol‐assisted APCVD (AA‐APCVD) . The functional optoelectronic applications of such layers include thin‐film transistors, thin‐film solar cells, c‐Si surface passivation layers, and patterned films via imprinting .…”

“…As the dish is heated, the ink evaporates forming a vapor within the space enclosed by the dish that is composed of three species, namely the different silanes, silicon hydride polymers, and Si‐NP. The contribution to film growth from the first two likely takes place via a combination of pyrolytic decomposition reactions and conversion (cross‐linking) into a‐Si:H at the surface of the substrate, respectively . Their presence also helps lower the effective thermal decomposition temperature of the ink and hence increase the film growth rate during APCVD .…”