On the formation process of luminescing centers in spark-processed silicon

Ludwig, Matthias; Augustin, A.; Hummel, Rolf E.; Groß, Th.

doi:10.1063/1.363470

Cited by 19 publications

(8 citation statements)

References 29 publications

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“…In general, previous estimates by Hummel and co-workers suggest that for a 15 kV spark there is ϳ7 mJ of ohmic energy associated with each sparking event of ϳ10 nanoseconds duration. 16 Using an appropriate high voltage probe, we find that the 3.2 mm gap described above produces a 7 kV spark ͑peak-to-peak͒, clearly of sufficient energy to ablate the Si. Increasing the gap to 9.5 mm results in an increased spark energy of 19 kV.…”

mentioning

confidence: 89%

The Use of Spark Ablation to Produce Calcium Phosphate Films on Silicon

Weis¹,

Chen²,

Coffer³

2002

Electrochem. Solid-State Lett.

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A method for fabrication of calcium phosphate films on crystalline silicon substrates which employs a high energy dc spark on silicon surfaces in the presence of Ca 10 ͑PO 4 ͒ 6 ͑OH͒ 2 is described. Such a process kinetically traps the desired calcium phosphate on the substrate with concomitant formation of a porous layer. Scanning electron micrographs of the silicon substrate show a nanoporous surface morphology for those areas exposed to spark processing. Energy dispersive X-ray analysis and infrared vibrational spectroscopy of the spark-processed regions of the Si substrate are clearly consistent with the presence of the desired biologically relevant material. In conjunction with an automated stage, facile formation of deliberate micrometer-size patterns is demonstrated.While long considered as the paradigm of semiconductor microelectronics, crystalline silicon ͑Si͒ has, with few exceptions, received minimal attention for its potential as a biomaterial. 1-4 Recent efforts by Canham and co-workers have clearly demonstrated that one approach to induce bioactivity in Si is to electrochemically form nanoporous Si films followed by the cathodic growth of calcium phosphate ͑the common inorganic mineral phase of bone͒. 5-7 Such materials are attracting attention as possible drug delivery vehicles 8,9 and a host of other applications. 10 As an alternative to the anodic etch process, previous studies have shown that the high-frequency arc from a Tesla coil can ablate the surface of crystalline silicon, producing nanoporous surfaces. [11][12][13] It has also been subsequently demonstrated that if a rare earth salt is deposited on the silicon surface and then spark processed, the resulting Si porous layer is doped with ''clusters'' of rare earth ions coordinated to oxygen. 14,15 These latter studies suggest that it should be possible to kinetically trap a variety of useful, thermally stable materials as the ablated Si coalesces onto the surface. Thus, this paper describes the use of a spark ablation process to produce calcium phosphate films anchored to Si. These materials are characterized via scanning electron microscopy ͑SEM͒, energy dispersive X-ray analysis ͑XEDS͒, and infrared vibrational spectroscopy ͑FTIR͒. These results confirm that the porous spark-processed regions of the substrate are clearly consistent with the presence of the desired biologically relevant material. The impact of electrode gap and spark duration, parameters that most sensitively determine film thickness and composition, are also discussed.Square pieces (15 ϫ 15 mm) of p-type, ͗100͘, boron-doped Czochralski ͑CZ͒ Si ͑6-8 ⍀ cm͒ were employed in these experiments. Electrical contact was achieved using Ni wire and silver epoxy. An excess of Ca 10 ͑PO 4 ͒ 6 ͑OH͒ 2 ͑Aldrich͒ is deposited on the wafer surface by either a slurry in acetone ͑or water͒ or alternatively by direct application of the dry calcium phosphate powder onto the surface with compression by a glass rod. The sample was allowed to dry, producing a layer of calcium phosphate covering...

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confidence: 89%

The Use of Spark Ablation to Produce Calcium Phosphate Films on Silicon

Weis¹,

Chen²,

Coffer³

2002

Electrochem. Solid-State Lett.

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“…Besides erosive surface techniques widely used to process bulk silicon [2,3], there is growing interest in gas phase synthesis of nanosized Si particles which, by embedding them in a passivating matrix, may be stabilised against influences of the ambient. Various methods of synthesis are reported ranging from co-sputtering of Si and silica, ion implantation of Si into silica, laser ablation and gas phase evaporation of silicon to plasmaassisted decomposition of silane [4][5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Lattice contraction in nanosized silicon particles produced by laser pyrolysis of silane

Hofmeister

Huisken

Kohn

1999

The European Physical Journal D

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We used laser-induced decomposition of silane for the fabrication of nanosized Si particles and studied in detail their structural characteristics by conventional and high resolution electron microscopy. The silane gas flow reactor incorporated in a molecular beam apparatus was operated without size selection to achieve a broad size distribution. Deposition at low energy on carbon substrates yielded single crystalline, spherical Si particles almost completely free of planar lattice defects. The particles, covered by thin amorphous oxide shells, are not agglomerated into larger aggregates. The lattice of diamond cubic type exhibits deviations from the bulk spacing which vary from distinct contraction to dilatation as with decreasing particle size the oxide shell thickness is reduced. This effect is discussed in terms of the strong Si/oxide interfacial interaction and compressive stresses arising upon oxidation. A negative interface stress, as determined from the size dependence of the lattice spacing, limits the curvature of the interface, i.e., at small sizes Si oxidation must be considered as a self-limiting process.

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“…Besides erosive surface techniques applied to compact Si materials [5,6], there is growing interest in the fabrication of particulate silicon showing comparable properties. By embedding in a passivating matrix, these materials are designed to achieve stability against aects of any ambient conditions.…”

Section: Introductionmentioning

confidence: 99%

Structure of nanometersized silicon particles prepared by various gas phase processes

Hofmeister

Ködderitzsch

Dutta

1998

Journal of Non-Crystalline Solids

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We have explored various gas phase processes for the fabrication of nanometersized Si and SiO x particles and measured their structural properties (agglomeration, size, shape, crystallinity, surface roughness and internal structure) by conventional and high resolution electron microscopy. Agglomerated amorphous Si particles, 10±30 nm in size, were prepared by gas phase reactions including cluster growth processes in a low pressure silane plasma. Annealing at 900°C resulted in almost complete crystallisation of nearly spherical particles covered by an amorphous oxide shell. Inert gas arc evaporation of silicon yielded single crystalline, spherical Si particles, 4±16 nm in size, in which no defects were detected. These particles, agglomerated into chains and tangles, are covered entirely by a thin amorphous oxide layer. Thermal evaporation of solid SiO in an inert gas atmosphere produced agglomerated, nearly spherical amorphous SiO x particles, 8±24 nm in size, with considerable surface roughness. Upon annealing at 900°C, the formation of 3±6 nm sized Si crystallites in the interior of these particles was observed. Ó

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On the formation process of luminescing centers in spark-processed silicon

Cited by 19 publications

References 29 publications

The Use of Spark Ablation to Produce Calcium Phosphate Films on Silicon

The Use of Spark Ablation to Produce Calcium Phosphate Films on Silicon

Lattice contraction in nanosized silicon particles produced by laser pyrolysis of silane

Structure of nanometersized silicon particles prepared by various gas phase processes

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