Growth of Ge, Si, and SiGe nanocrystals in SiO2 matrices

Zhu, Jane G.; White, C.W.; Budai, J. D.; Withrow, S. P.; Chen, Y.

doi:10.1063/1.359843

Cited by 186 publications

(57 citation statements)

References 16 publications

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“…Visible PL has been observedl from Si nanocrystals, or quantum dots, produced by a variety of techniques including aerosols,2 colloids,3 and ion implantation. 4 However, all of these techniques produce large distributions of cluster sizes resulting in broad, unstructured optical absorption and PL features which limit usefulness and make definitive interpretation of results difficult.…”

mentioning

confidence: 99%

Tailorable, visible light emission from silicon nanocrystals

Wilcoxon¹,

Samara²

1999

Applied Physics Letters

178

121

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Crystalline, size-selected Si nanocrystals in the size range 1.8-10 nm grown in inverse micellar cages exhibit highly structured optical absorption and photoluminescence (PL) across the visible range of the spectrum. The most intense PL for the smallest nanocrystals produced (-2 nm) was in the blue (-365 nm) with a radiative lifetime of -1 ns and is attributed to direct recombination at zone center. There is presently a large research effort aimed at exploring physical and chemical means to induce a useful level of visible photoluminescence (PL) from silicon (Si). The approaches includel porous silicon and quantum wires and dots. These two approaches, which may be mechanistically related via quantum confinement, have considerable potential but are poorly understood. Visible PL has been observedl from Si nanocrystals, or quantum dots, produced by a variety of techniques including aerosols,2 colloids,3 and ion implantation.4 However, all of these techniques produce large distributions of cluster sizes resulting in broad, unstructured optical absorption and PL features which limit usefulness and make definitive interpretation of results difficult. DISCLAIMERWe have used inverse micelles as reaction vessels5 to produce useful quantities of Si nanocrystals which have been remarkable in their size monodispersity, the sharpness and richness of their spectral features and tailorability of their properties.In what follows we describe the synthesis and some of the properties. Details of the work will be published elsewhere.6 An anhydrous ionic salt (e.g., SiX4, where X = Cl, Br, or I) is dissolved in the hydrophilic interior of a solution of micelles in octane with complete absence of water. The surfactants used, nonionic aliphatic pol yethers or quatemary ammonium cationic surfactants, are dissolved in anhydrous tetrahydro furan (THF) and dried over Na metal. We next reduce Si(IV)to Si(0) using an anhydrous metal hydride, (usually 1M LiAl~in THF). The reduction is rapid with vigorous bubbling of Hz gas. One can determine the progress of the reaction by following the disappearance of the Si(IV) charge transfer absorption from the precursor solution.Nanocrystals with diameters between 1.8 and -10 nm were produced. Spectroscopy and high pressure liquid chromatography (HPLC) with on-line absorbance, conductivity and refractive index detectors were used to demonstrate 100% reduction of the Si(IV) to the final Si (0) nanocrystal form. The nanocrystals were characterized by high-resolution transmission electron microscopy.The optical absorption spectra of our nanocrystals are much richer in spectral features than earlier nanocrystal spectra making it possible to assess the role of quantum confinement inSi. An example is shown in Fig. 1 for a sample of 2 nm nanocrystals. The figure also shows the spectrum of bulk Si where the spectral features reflect the details of the band structure shown in the inset in Fig. 2. Specifically, the long absorption tail between 1. The close resemblance in the shape of the two spectra in F...

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mentioning

confidence: 99%

Tailorable, visible light emission from silicon nanocrystals

Wilcoxon¹,

Samara²

1999

Applied Physics Letters

178

121

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“…To further enhance the previous discussions on property-structure relationships, other microstructure characterization techniques such as TEM (Transmission Electron Microscopy) (Zhu et al 1995;Min et al 1996;Gourbilleau et al 2001;Werwa et al 1994;Inokuma et al 1998;lacona et al 2000) would be required in the future work. In particular, a special TEM technique named Energy Filtered Transmission Electron Microscopy (EFTEM) appears to be most promising (lacona et al 2004).…”

Section: Discussionmentioning

confidence: 99%

“…In this project, three other characterization techniques were utilized to enhance the previous discussions on property-structure relationships, including FTIR spectroscopy ( Other characterization techniques may be useful for the future directions of research on this topic, such as Transmission Electron Microscopy (TEM) (Transmission Electron Microscopy) (Zhu et al 1995;Min et al 1996;Gourbilleau et al 2001;Werwa et al 1994;Inokuma et al 1998;lacona et al 2000).…”

Section: Materials Characterizationmentioning

confidence: 99%

Residual Stress and Fracture of PECVD Thick Oxide Films for Power MEMS Structures and Devices

Zhang¹

2007

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, seerching data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Washington Headquarters Service, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and SUPPLEMENTARY NOTES14. ABSTRACT Plasma enhanced chemical vapor deposited (PECVD) silicon oxide (SiOx) is the most commonly used interlayer dielectric (ILD) in MEMS devices and structures. In this project, PECVD SiOx is chosen as an example for the systematic study of mechanical behavior and underlying casual mechanisms of amorphous thin films for MEMS applications, which are generally less well understood because of the complex interplay among the deformation mechanisms. In this project, PECVD SiO, is chosen as an example for the systematic study of mechanical behavior and underlying causal mechanisms of amorphous thin films for MEMS applications, which are generally less well understood because of the complex interplay among the deformation mechanisms. SUBJECT TERMSMechanical behaviors of the PECVD SiOx thin films are probed at 1) different size scales (from wafer level down to micro/nano-scale, and different lengthscale within each realm); 2) different temperatures (from room temperature up to 1100 0C); and 3) with a combination of different experimental techniques (such as substrate curvature measurements, nanoindentation tests, and a novel "microbridge testing" technique, etc.). A broad range of mechanical analysis is covered, including film stress and related material properties changes, elastic properties, plastic properties (both time-independent and time-dependent), deformation mechanisms (both at room temperature and elevated temperatures).Wherever applicable, materials analysis techniques such as SEM, AFM, FTIR, XRD, and SIMS were employed to strengthen the discussions on the structureproperties relationship and the causal mechanisms of the mechanical responses of the PECVD SiOx. These experiments reveal various interesting arid disiirictive characteristics of the mechanical responses of the PECVD SiOx thin films, and the microstructural causal mechanisms for each of them are analyzed in depth.The outcome of this work will provide a comprehensive characterization of the mechanical responses of the PECVD SiOx thin films under different thermal conditions, stress levels, size scales, and in both elastic and plastic regions. In addition, both new experimental methodologies and theoretical models for data 3 analysis are resulted, which can be readily applied to a wide variety of thin film materials for various different applications. Last but not least, the physical causal mechanisms for the experimental results are elucidated, ...

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“…In this way, HRTEM, X-ray diffraction and Raman spectroscopy have been used. In addition, these optical properties show significant changes due to a subsequent thermal annealing process [11][12][13].…”

Section: Introductionmentioning

confidence: 98%

Structural evolution of nanocrystalline silicon studied by high resolution transmission electron microscopy

Ponce

Benami

Santana

et al. 2007

Phys. Status Solidi (c)

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In this work, nanocrystalline silicon (nc-Si) embedded in amorphous silicon nitride (a-SixNy) films have been characterized by High Resolution Transmission Electron Microscopy (HRTEM). The films have been grown by remote plasma enhanced chemical vapour deposition (RPECVD) onto silicon substrates using a mixture of SiCl 4 , NH 3 and H 2 . Subsequently, the sample has been introduced to an annealed process. The nanocrystalline inclusions have been measured from the analysis of HRTEM images. The size of nc-Si inclusions is modified due to the annealing process. The diameter of nc-Si inclusions in as-grown films vary from 1.3 to 3.1 nm. In annealed films, a high density of new clusters with reduction of 1 nm of those diameters is observed, as well as the coalescence phenomenon among some nc-Si inclusions is observed too. Consequently, the diameters of annealed films nc-Si inclusions range from 0.7 to 4 nm. The thin films show an excellent photoluminescence emission. The density per unit area and size of the nc-Si inclusions are correlated with the PL emissions. The influence of the structural changes of the nc-Si on the PL emissions is discussed.

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Growth of Ge, Si, and SiGe nanocrystals in SiO2 matrices

Cited by 186 publications

References 16 publications

Tailorable, visible light emission from silicon nanocrystals

Tailorable, visible light emission from silicon nanocrystals

Residual Stress and Fracture of PECVD Thick Oxide Films for Power MEMS Structures and Devices

Structural evolution of nanocrystalline silicon studied by high resolution transmission electron microscopy

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