Self-organization of ammonium silicon hexafluoride complex low-dimensional structures on Silicon

Kalem, Ş.

doi:10.1016/j.spmi.2008.07.003

Cited by 6 publications

(19 citation statements)

References 13 publications

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“…However, we find out that these patterns could well be the signature of an hexagonal αphase quartz-like GeO 2 crystalline structure. The diffraction peaks observed in XRD spectrum 5 of our sample are indeed very closely matching those of α-GeO 2 quartz-like crystal structure by 1% difference according to data provided in literature [13][14][15][16]. This suggests that there is a dominant contribution from the crystalline oxide clusters to the diffraction patterns.…”

Section: Resultssupporting

confidence: 88%

“…For the formation mechanism of the germanates under acid vapor treatment, the transformation can be described using the following overall chemical reaction by taking into account the final products, that is the fluogermanate (NH 4 ) 2 GeF 6 and the germanium oxide GeO 2 as observed by XRD, EDS and FTIR measurements: However, by analogy to previous works, one can suggest that the transformation process starts with oxidation of Germanium and the etching of the oxide by HF [5,6]. Similar initial reaction pathways have been suggested by several research groups in chemical etching experiments of Silicon [6][7][8][9][10].…”

Section: Resultsmentioning

confidence: 99%

“…This topic has been the focus of research interest for the unique optical and structural properties and for the possibility of application of the resulting material [2][3][4]. The presence of a cryptocrystalline structure soaking all the visible light, photoluminescence emission, self-assembly of low-dimensional structures and the possible applications as a dielectric insulation material in integrated circuits are among interesting features [2,5]. It is of crucial importance to see if Germanium (Ge), another element of the same periodic group (IV) could be undergone similar surface modification under an acid vapor exposure consisting of HF and HNO 3 .…”

Section: Introductionmentioning

confidence: 99%

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Transformation of germanium to fluogermanates

2009

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The surface of a single crystal Germanium wafer was transformed to crystals of germanium fluorides and oxides upon exposure to a vapor of HF and HNO3 chemical mixture. Structure analysis indicate that the transformation results in a germanate polycrystalline layer consisting of germanium oxide and ammonium fluogermanate with a preferential crystal growth orientation in <101> direction. Local vibrational mode analysis confirms the presence of N-H and Ge-F vibrational modes in addition to Ge-O stretching modes. Energy dispersive studies reveal the presence of hexagonal {\alpha}-phase GeO2 crystal clusters and ammonium fluogermanates around these clusters in addition to a surface oxide layer. Electronic band structure as probed by ellipsometry has been associated with the germanium oxide crystals and disorder induced band tailing effects at the interface of the germanate layer and the bulk Ge wafer. The acid vapor exposure causes Ge surface to emit a yellow photoluminescence at room temperature

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Section: Resultssupporting

confidence: 88%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Transformation of germanium to fluogermanates

2009

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“…1). Thus, the pillars have been thinned down to 175 nm from nm (pillar width at half-height) by the transformation of the pillar surfaces to an intermediate oxide layer followed by the growth of a sacrificial layer of ASH [22][23][24], which could be removed by rinsing the pillars in water. We observe that the core of Si nanopillars is still crystalline as evidenced by Bragg reflections (dark regions in Fig.…”

Section: Resultsmentioning

confidence: 99%

Controlled thinning and surface smoothening of silicon nanopillars

Kalem¹,

Werner²,

Nilsson³

et al. 2009

Nanotechnology

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A convenient method has been developed to thin electron beam fabricated silicon nanopillars under controlled surface manipulation by transforming the surface of the pillars to an oxide shell layer followed by the growth of sacrificial ammonium silicon fluoride coating. The results show the formation of an oxide shell and a silicon core without significantly changing the original length and shape of the pillars. The oxide shell layer thickness can be controlled from a few nanometers up to a few hundred nanometers. While downsizing in diameter, smooth Si pillar surfaces of less than 10 nm roughness within 2 microm were produced after exposure to vapors of HF and HNO3 mixture as evidenced by transmission electron microscopy (TEM) analysis. The attempt to expose for long durations leads to the growth of a thick oxide whose strain effect on pillars can be assessed by coupled LO-TO vibrational modes of Si-O bonds. Photoluminescence (PL) of the pillar structures which have been downsized exhibits visible and infrared emissions, which are attributable to microscopic pillars and to the confinement of excited carriers in the Si core, respectively. The formation of smooth core-shell structures while reducing the diameter of the Si pillars has a potential in fabricating nanoscale electronic devices and functional components.

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“…But, the contribution from the ASH-Si interface is underestimated. Actually, the presence and the role of the interface layer (porous SiO x ) have already been described and its luminescent emission properties were investigated [1,4,7]. However, the likely incorporation of luminescent defect centers into the fluoride layer during the transformation process and the microscopic origin of the PL remain to be speculative and thus it needs to be explained in further detail.…”

Section: Introductionmentioning

confidence: 99%

Photoluminescence from silicon nanoparticles embedded in ammonium silicon hexafluoride

Kalem¹,

Werner²,

Talalaev³

et al. 2010

Nanotechnology

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Silicon (Si) nanoparticles (NPs) were synthesized by transforming a Si wafer surface to ammonium silicon hexafluoride (ASH) or (NH(4))(2)SiF(6) under acid vapor treatment. Si-NPs which were found to be embedded within the polycrystalline (ASH) layer exhibit a strong green-orange photoluminescence (PL). Differential PL measurements revealed a major double component spectrum consisting of a broad band associated with the ASH-Si wafer interfacial porous oxide layer and a high energy band attributable to Si-NPs embedded in the ASH. The origin of the latter emission can be explained in terms of quantum/spatial confinement effects probably mediated by oxygen related defects in or around Si-NPs. Although Si-NPs are derived from the interface they are much smaller in size than those embedded within the interfacial porous oxide layer (SiO(x), x > 1.5). Transmission electron microscopy (TEM) combined with Raman scattering and Fourier transformed infrared (FTIR) analysis confirmed the presence of Si-NP and Si-O bondings pointing to the role of oxygen related defects in a porous/amorphous structure. The presence of oxygen of up to 4.5 at.% in the (NH(4))(2)SiF(6) layer was confirmed by energy dispersive spectroscopy (EDS) analysis.

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Self-organization of ammonium silicon hexafluoride complex low-dimensional structures on Silicon

Cited by 6 publications

References 13 publications

Transformation of germanium to fluogermanates

Transformation of germanium to fluogermanates

Controlled thinning and surface smoothening of silicon nanopillars

Photoluminescence from silicon nanoparticles embedded in ammonium silicon hexafluoride

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