Showing papers by "Xiang Zhang published in 2005"
TL;DR: This work demonstrated sub–diffraction-limited imaging with 60-nanometer half-pitch resolution, or one-sixth of the illumination wavelength, using silver as a natural optical superlens and showed that arbitrary nanostructures can be imaged with good fidelity.
Abstract: Recent theory has predicted a superlens that is capable of producing sub–diffraction-limited images. This superlens would allow the recovery of evanescent waves in an image via the excitation of surface plasmons. Using silver as a natural optical superlens, we demonstrated sub–diffraction-limited imaging with 60-nanometer half-pitch resolution, or one-sixth of the illumination wavelength. By proper design of the working wavelength and the thickness of silver that allows access to a broad spectrum of subwavelength features, we also showed that arbitrary nanostructures can be imaged with good fidelity. The optical superlens promises exciting avenues to nanoscale optical imaging and ultrasmall optoelectronic devices.
3,753 citations
TL;DR: In this article, a high-resolution projection micro-stereolithography (PμSL) process by using the Digital Micromirror Device (DMD™, Texas Instruments) as a dynamic mask is presented.
Abstract: We present in this paper the development of a high-resolution projection micro-stereolithography (PμSL) process by using the Digital Micromirror Device (DMD™, Texas Instruments) as a dynamic mask. This unique technology provides a parallel fabrication of complex three-dimensional (3D) microstructures used for micro electro-mechanical systems (MEMS). Based on the understanding of underlying mechanisms, a process model has been developed with all critical parameters obtained from the experimental measurement. By coupling the experimental measurement and the process model, the photon-induced curing behavior of the resin has been quantitatively studied. The role of UV doping has been thereafter justified, as it can effectively reduce the curing depth without compromising the chemical property of the resin. The fabrication of complex 3D microstructures, such as matrix, and micro-spring array, with the smallest feature of 0.6 μm, has been demonstrated.
760 citations
TL;DR: It is found that the intensity at the focal points of the plasmonic lenses increases with size, and the nearfield is mapped experimentally using nearfield scanning optical microscopy and plAsmonic lithography.
Abstract: We report the focusing of surface plasmon polaritons by circular and elliptical structures milled into optically thick metallic films or plasmonic lenses. Both theoretical and experimental data for the electromagnetic nearfield is presented. The nearfield is mapped experimentally using nearfield scanning optical microscopy and plasmonic lithography. We find that the intensity at the focal points of the plasmonic lenses increases with size.
546 citations
TL;DR: Simulation results show that one-dimensional and two-dimensional periodical structures of 40-100 nm features can be patterned using interfering surface plasmons launched by 1D gratings, which can go far beyond the free-space diffraction limit of the light.
Abstract: A new nanophotolithography technique based on the interference of surface plasmon waves is proposed and demonstrated by using computer simulations. The wavelengths of the surface plasmon waves at metal and dielectric interfaces can reach the nanometer scale while their frequencies remain in the optical range. As a result, the resolution of this surface plasmon interference nanolithography (SPIN) can go far beyond the free-space diffraction limit of the light. Simulation results show that one-dimensional and two-dimensional periodical structures of 40−100 nm features can be patterned using interfering surface plasmons launched by 1D gratings. Detailed characteristics of SPIN such as field distribution and contrast are also investigated.
360 citations
TL;DR: Fang et al. as discussed by the authors used a thin silver slab for superlensing and obtained an image of a 50 nm half-pitch object at λ 0/7 resolution, which is well below the diffraction limit.
Abstract: Recently, the concept of superlensing has received considerable attention for its unique ability to produce images below the diffraction limit. The theoretical study has predicted a 'superlens' made of materials with negative permittivity and/or permeability, is capable of resolving features much smaller than the working wavelength and a near-perfect image can be obtained through the restoration of lost evanescent waves (Pendry 2000 Phys. Rev. Lett. 85 3966–9). We have already demonstrated that a 60 nm half-pitch object can indeed be resolved with λ0/6 resolution with the implementation of a silver superlens with λ0 = 365 nm illumination wavelength, which is well below the diffraction limit (Fang et al 2005 Science 308 534–7). In order to further support the imaging ability of our silver superlens, a two-dimensional arbitrary object with 40 nm line width was also imaged (Fang et al 2005 Science 308 534–7). In this paper, we present experimental and theoretical investigations of optical superlensing through a thin silver slab. Experimental design and procedures as well as theoretical studies are presented in detail. In addition, a new superlens imaging result is presented which shows the image of a 50 nm half-pitch object at λ0/7 resolution.
131 citations
TL;DR: It is concluded that there is little redundancy among ESEs in an exon and that they must work in concert to optimize splicing.
Abstract: We have previously formulated a list of approximately 2,000 RNA octamers as putative exonic splicing enhancers (PESEs) based on a statistical comparison of human exonic and nonexonic sequences (X. H. Zhang and L. A. Chasin, Genes Dev. 18:1241-1250, 2004). When inserted into a poorly spliced test exon, all eight tested octamers stimulated splicing, a result consistent with their identification as exonic splicing enhancers (ESEs). Here we present a much more stringent test of the validity of this list of PESEs. Twenty-two naturally occurring examples of nonoverlapping PESEs or PESE clusters were identified in six mammalian exons; five of the six exons tested are constitutively spliced. Each of the 22 individual PESEs or PESE clusters was disrupted by site-directed mutagenesis, usually by a single-base substitution. Eighteen of the 22 disruptions (82%) resulted in decreased splicing efficiency. In contrast, 24 control mutations had little or no effect on splicing. This high rate of success suggests that most PESEs function as ESEs in their natural context. Like most exons, these exons contain several PESEs. Since knocking out any one of several could produce a severalfold decrease in splicing efficiency, we conclude that there is little redundancy among ESEs in an exon and that they must work in concert to optimize splicing.
124 citations
TL;DR: It is concluded that most exons require signals in their immediate flanks for efficient splicing and speculate that there may be different mechanisms for splice site recognition depending on G+C content.
Abstract: Intronic elements flanking the splice-site consensus sequences are thought to play a role in pre-mRNA splicing. However, the generality of this role, the catalog of effective sequences, and the mechanisms involved are still lacking. Using molecular genetic tests, we first showed that the approximately 50-nt intronic flanking sequences of exons beyond the splice-site consensus are generally important for splicing. We then went on to characterize exon flank sequences on a genomic scale. The G+C content of flanks displayed a bimodal distribution reflecting an exaggeration of this base composition in flanks relative to the gene as a whole. We divided all exons into two classes according to their flank G+C content and used computational and statistical methods to define pentamers of high relative abundance and phylogenetic conservation in exon flanks. Upstream pentamers were often common to the two classes, whereas downstream pentamers were totally different. Upstream and downstream pentamers were often identical around low G+C exons, and in contrast, were often complementary around high G+C exons. In agreement with this complementarity, predicted base pairing was more frequent between the flanks of high G+C exons. Pseudo exons did not exhibit this behavior, but rather tended to form base pairs between flanks and exon bodies. We conclude that most exons require signals in their immediate flanks for efficient splicing. G+C content is a sequence feature correlated with many genetic and genomic attributes. We speculate that there may be different mechanisms for splice site recognition depending on G+C content.
77 citations
TL;DR: Some of the methods used to discover functional splicing signals are described, including comparisons to "pseudo exons," intronic sequences resembling exons by virtue of being bounded by sequences indistinguishable from splice sites.
62 citations
TL;DR: In this article, the authors reported the ultrafast and large third-order nonlinear optical properties of CdS nanocrystals (NCs) embedded in a polymeric film.
Abstract: We report the ultrafast and large third-order nonlinear optical properties of CdS nanocrystals (NCs) embedded in a polymeric film. The CdS NCs of 2 nm radius are synthesized by an ion-exchange method and highly concentrated in the two layers near the surfaces of the polymeric film. The two-photon absorption coefficient and the optical Kerr coefficient are measured with laser pulses of 250 fs duration at 800 nm wavelength. The one-photon and two-photon figures of merit are determined to be 3.1 and 1.3, respectively, at irradiance of 2 GW/cm2. The observed nonlinearities have a recovery time of ∼1 ps. The two-photon-generated free carrier effects have also been observed and discussed. These results demonstrate that CdS NCs embedded in polymeric film are a promising candidate for optical switching applications.
61 citations
TL;DR: In this paper, a planar metallic mask was used for near-field optical lithography with half-pitch resolution up to 60nm using I-line (365nm) wavelength.
Abstract: The development of a near-field optical lithography is presented in this paper. By accessing short modal wavelengths of localized surface plasmon modes on a planar metallic mask, the resolution can be significantly increased while using conventional UV light source. Taking into account the real material properties, numerical studies indicate that the ultimate lithographic resolution at 20nm is achievable through a silver mask by using 365nm wavelength light. The surface quality of the silver mask is improved by adding an adhesion layer of titanium during the mask fabrication. Using a two-dimensional hole array silver mask, we experimentally demonstrated nanolithography with half-pitch resolution down to 60nm, far beyond the resolution limit of conventional lithography using I-line (365nm) wavelength.
54 citations
TL;DR: In this paper, the authors derived closed-form scaling formulas for strain in embedded lattice-mismatched spherical quantum dots and extended them to cubic anisotropy and arbitrary shape.
Abstract: Both quantitative and qualitative knowledge of strain and strain distributions in quantum dots are essential for the determination and tailoring of their optoelectronic properties. Typically strain is estimated using classical elasticity and then coupled to a suitable band structure calculation approach. However, classical elasticity is intrinsically size independent. This is in contradiction to the physical fact that at the size scale of a few nanometers, the elastic relaxation is size dependent and a departure from classical mechanics is expected. First, in the isotropic case, based on the physical mechanisms of nonlocal interactions, we herein derive (closed-form) scaling formulas for strain in embedded lattice-mismatched spherical quantum dots. In addition to a size dependency, we find marked differences in both spatial distribution of strain as well as in quantitative estimates especially in cases of extremely small quantum dots. Fully recognizing that typical quantum dots are neither of idealized spherical shape nor isotropic, we finally extend our results to cubic anisotropy and arbitrary shape. In particular, an exceptionally simple expression is derived for the dilation in an arbitrary shaped quantum dot. For the more general case (incorporating anisotropy), closed-form results are derived in the Fourier space while numerical results are provided to illustrate the various physical insights. Apart from qualitative and quantitative differences in strain states due to nonlocal effects, an aesthetic by-product for the technologically important polyhedral shaped quantum dots is that strain singularities at corners and vertices (which plague the classical elasticity formulation) are absent. Choosing GaAs as an example material, our results indicate that errors as large as hundreds of meV may be incurred upon neglect of nonlocal effects in sub-10-nm quantum dots.
TL;DR: In this paper, an investigation on fatigue crack growth behavior and fail safety of integral stringer panels typified by welded aircraft fabrications is presented, where numerical simulations are performed for two configurations, two-stringer and ninestringer panels, and three damage scenarios, in which weldinginduced longitudinal residual stresses are taken into account.
Abstract: An investigation is presented on fatigue crack growth behavior and fail safety of integral stringer panels typified by welded aircraft fabrications. The stringer panel is made of aluminum alloy 2024-T351 and fabricated by the variable-polarity plasma-arc welding process. The sample simulates a part of the lower-wing skin structures. Based on the linear elastic fracture mechanics, numerical simulations are performed for two configurations, two-stringer and nine-stringer panels, and three damage scenarios, in which welding-induced longitudinal residual stresses are taken into account. A typical load spectrum for large transport aircraft is employed for the analysis. For the two-stringer panel life predictions have a reasonably good correlation with the test results. Based on this validation, large-scale nine-stringer panels with three manufacture options, that is, riveted, integrally machined, and welded integral, are simulated for a skin crack under a broken central stringer propagating to two-bay length. Useful comparisons are made among the three variants. Finally, remedies to improve damage tolerance and fail safety of integral stringer panels are explored. The incorporation of crack retarder straps bonded to the inner surface of an integral panel has greatly improved the fail safety behavior of the component with dramatically increased crack growth live.
TL;DR: A method for thin-film fabrication employing high oxygen-pressure processing (HOPP) was developed in this paper, where the highly oriented Pb(ZrxTi1−x)O3 (PZT) thin film was fabricated at temperature as low as 400°C.
Abstract: A method for thin-film fabrication employing high oxygen-pressure processing (HOPP) was developed With this method, the highly (100) oriented Pb(ZrxTi1−x)O3 (PZT) thin film was fabricated at temperature as low as 400°C HOPP is compatible to the ferroelectric PZT film integration with a readout integrated circuit The sol-gel-derived PZT 50∕50 thin film showed a well-saturated hysteresis loop at an applied electric field of 367kV∕cm with Pr and Ec of 45μC∕cm2 and 121kV∕cm, respectively Large electric leakage was attributed to remnant organic components, which was demonstrated by sputtered organic-free PZT films The optimized Pr and Ec are of 26μC∕cm2 and 93kV∕cm under an applied electric field of 400kV∕cm
TL;DR: In this article, the transmission of evanescent waves through thin films of increasing thickness was investigated using natural roughness as a well characterized grating, and it was shown that evanescence wave transmission rapidly grows with film thickness up to about 50 nm, after which it decays as loss becomes significant.
Abstract: In this paper, we investigated an essential precursor of superlensing: enhancing the transmission of evanescent waves assisted by excitation of surface plasmon. Using natural roughness as a well characterized grating, the transmission of evanescent waves is studied through silver thin films of increasing thickness. Measurements and calculations are performed in the wavelength range of 514.5 nm to 351.1 nm where the real part of the permittivity of silver is negative. Pronounced peaks due to surface-plasmon excitations are observed in the transmission spectra. We found the transmission of evanescent waves rapidly grows with the film thickness up to about 50 nm, after which it decays as loss becomes significant. As the permittivity of a silver slab approaches -1, we experimentally observed a broadening of surface plasmon bandwidth. Our study indicates a pathway to access the deep subwavelength features by metamaterial superlens.
TL;DR: If the pump laser frequency is tuned near a photonic band edge and the atomic system is carefully chosen such that the Stokes mode matches another photonicBand edge, low-threshold, enhanced Raman amplification is possible.
Abstract: We study the stimulated Raman scattering (SRS) of light from an atomic system embedded in a photonic crystal and coherently pumped by a laser field. In our study, the electromagnetic field is treated classically and the atomic system is described quantum mechanically. Considering a decomposition of the pump and Stokes fields into the Bloch modes of the photonic crystals and using a multiscale analysis, we derive the Maxwell-Bloch equations for SRS in photonic crystals. These equations contain effective parameters that characterize the SRS gain, the nonlinear atomic response to the electromagnetic field, and the group velocity and that can be calculated in terms of the Bloch modes of the unperturbed photonic crystal. We show that if the pump laser frequency is tuned near a photonic band edge and the atomic system is carefully chosen such that the Stokes mode matches another photonic band edge, low-threshold, enhanced Raman amplification is possible. Possible physical realizations of SRS in photonic crystals are also discussed.
TL;DR: In this paper, the propagation of an electromagnetic (EM) wave in a piezomagnetic superlattice was studied, and the coupling between the EM wave and the vibration of super lattice was established, resulting in the creation of a type of magnetic polariton that does not exist in ordinary magnetic material.
Abstract: We studied the propagation of an electromagnetic (EM) wave in a piezomagnetic superlattice with piezomagnetic coefficient being modulated. Because of the piezomagnetic effect, the coupling between the EM wave and vibration of superlattice can be established, resulting in the creation of a type of magnetic polariton that does not exist in ordinary magnetic material. At some resonance frequencies, the abnormality of dispersion of permeability introduces negative value and piezomagnetic superlattice can make a kind of negative permeability material.
TL;DR: In this article, the structural and magnetic properties of Pr0.75Na0.25MnO3 have been investigated experimentally and it was shown that the Mn3+ and Mn4+ cations form zigzag chains in a c plane by analyzing the diffraction patterns.
TL;DR: In this article, the authors studied the propagation of an electromagnetic (EM) wave in piezoelectric-piezomagnetic multilayers, in which the incident EM wave excites high frequency acoustic waves and couples strongly with them through dielectric polariton and magnetic polariton simultaneously.
Abstract: We study the propagation of an electromagnetic (EM) wave in piezoelectric–piezomagnetic multilayers, in which the incident EM wave excites high frequency acoustic waves and couples strongly with them through piezoelectric and piezomagnetic effects, creating dielectric polariton and magnetic polariton simultaneously. The dispersion abnormality appears at some frequency ranges where simultaneous negative permittivity and permeability can be achieved. Theoretical analysis and numerical simulation proved that this structure forms a kind of “left-handed” material.
TL;DR: In this paper, the authors showed that the 120 nm-thick silver film does not help to record an image of the mask and that the image is likely due to an overexposure.
Abstract: Melville, Blaikie, and Wolf reported a submicron imaging using a 120-nm-thick silver slab. Diffraction-limited features as small as 350 nm sat a 700 nm period d were imaged onto the photosensitive material with the silver slab. The image resolution is said to be improved compared to a control experiment with 120 nm of poly smethylmethacrylate d sPMMAd between the mask and the photoresist wi hout silver filmd. Despite an extensive and intended connection to the superlens theory 2 throughout the letter and the following news thereof, 3 this experiment in our opinion is irrelevant to the referred superlens theory. This comment clarifies the interpretation of the experiment reported by Melville et al. Regarding the work reported in Ref. 1, we believe that the 120 nm silver film does not help to record an image of the mask. As we will show, the transmission behavior through this thick silver film shows that incident waves are strongly attenuated for all near field features including propagating and evanescent waves, thus the system does not enhance any evanescent waves as a superlens does. The blurred image recorded by the control experiment is in our opinion likely due to an excessive exposure. The basic theoretical idea suggested by Pendry 2 is based on the potential of a silver film to transmit and strongly enhance evanescent waves which carry subwavelength informationsoriginally scattered by the mask d. This so-called superlensing effect may be used to rebuild a subwavelength image. 4 But because the minimum feature size of the mask in this experiment is about the incident wavelength, the imaging reconstruction of the mask does not require a subwavelength imaging method, in other words, is not relevant to a superlens that significantly enhances evanescent waves scattered by the object. In Fig. 1, we calculate the transmission transfer function of TM wavesslike in the experiment Fig. 1 of Ref. 1 d for a 120 nm silver at 365 nm wavelength, which is the amplitude ratio of the transmitted H field over the incident H field as a function of the transverse wave number. It can be seen that the 120 nm silver film actually acts like an attenuator. For instance, for the 700 nm period object, the corresponding incident propagating waves have only less than 1% of the transmitted intensity. More importantly, this 120 nm silver film does not enhance evanescent waves. Since a broadband wavelength of 300–450 nm is used in Ref. 1 as described in detail in Ref. 5, we further found that the transmission for 300–450 nm has very similar behavior as 365 nm. A superlens effect is expected only for wavelength longer than 400 nm for the system used in Ref. 1 for a very narrow band of transverse wave number corresponding to evanescent waves that cannot be generated by the mask in the experiment of Ref. 1. A blurred optical image shown Fig. 2 sad of Ref. 1 is obtained by a control experiment using the same thickness of PMMA s120 nmd but without silver film. In contrast, the image obtained using a silver film sandwiched between two 60 nm layers of PMMA is in agreement with the mask topography. According to Melvilleet al., the image is blurred because of diffraction effect in the PMMA. In our opinion, the blurred image is likely due to an overexposure. We note that a comparable exposure time of 2 min is used in both the experiment with silver and the control experiment. In the control experiment, the transmission will be significantly higher than the experiment with silver where less than 1% of the energy is transmitted through this silver film. We think that the appropriate exposure time used in the control experiment should be drastically reduced to obtain a good image. Therefore, the blurred image in the control experiment cannot serve as a trustworthy verification or confirmation in Ref. 1. Despite the very low transmission factor of waves through this thicks120 nmd silver, the recorded image shown in Fig. 2sbd of Ref. 1 is in agreement with the mask topog-
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TL;DR: It is shown that CdS NCs embedded in polymeric film are a promising candidate for optical switching applications and have a recovery time of approximately 1 ps.
Abstract: We report the ultrafast and large third-order nonlinear optical properties of CdS nanocrystals (NCs) embedded in a polymeric film. The CdS NCs of 2-nm radius are synthesized by an ion exchange method and highly concentrated in the two layers near the surfaces of the polymeric film. The two-photon absorption coefficient and the optical Kerr coefficient are measured with laser pulses of 250-fs duration at 800-nm wavelength. The one-photon and two-photon figures of merit are determined to be 3.1 and 1.3, respectively, at irradiance of 2 GW/cm2. The observed nonlinearities have a recovery time of ~ 1 ps. The two-photon-generated free carrier effects have also been observed and discussed. These results demonstrate that CdS NCs embedded in polymeric film are a promising candidate for optical switching applications.
25 Mar 2005
TL;DR: In this paper, S and P polarized measurements of artificial bianisotropic magnetic metamaterials with resonant behavior at infrared frequencies are presented, and the effects of bianismotropy on negative index are detailed and shown to be beneficial for certain configurations of the material parameters.
Abstract: We present S and P polarized measurements of artificial bianisotropic magnetic metamaterials with resonant behavior at infrared frequencies. These metamaterials consist of an array of micron sized (~40μm) copper rings fabricated upon a quartz substrate. Simulation of the reflectance is obtained through a combination of electromagnetic eigenmode simulation and Jones matrix analysis, and we find excellent agreement with the experimental data. It is shown that although the artificial magnetic materials do indeed exhibit a magnetic response, care must be taken to avoid an undesirable electric dipole resonance, due to lack of reflection symmetry in one orientation. The effects of bianisotropy on negative index are detailed and shown to be beneficial for certain configurations of the material parameters.
TL;DR: 3D proton plans based on the CT obtained by averaging the 3D CTs comprising the 4D CT, and with the CT numbers in the tumor volume replaced by the corresponding MIP CT numbers, is an effective approach to achieve good tumor coverage and acceptable normal tissue sparing.
Abstract: Purpose: Traditional treatment planning methods may lead to lung proton treatment plans in which the apparent and actual dose distributions may be significantly different due to respiratory motion. We are developing strategies for designing compensator-based 3D proton treatment plans using 4D CTs (composed of 3D CTs at a sequence of respiratory phases) for mobile lung tumors and assessing the validity of these strategies using 4D dose computation methods. Method and Materials: 4D CTs for a population of lung cancer patients were used to obtain tumor targets and critical structures. The internal target volume (ITV) was the composite of target volumes on the 4D CT. For each patient, we evaluated four compensator design and planning strategies based on (1) the average CT obtained by averaging all phases of the 4D CT; (2) free breathing CT; (3) maximum intensity projection (MIP) CT; and (4) the average CT with the CT numbers inside the tumor volume replaced by the corresponding MIP CT numbers. For each strategy, the resulting apparent dose distribution was compared with the corresponding 4D dose distribution computed by deforming dose distributions of each phase to the reference phase and summing. Results: The composite 4D dose coverage of the target was significantly superior for method (4) while normal tissue doses were slightly higher though well below the limits. A seemingly conservative compensator design using MIP for the entire image, not just the target volume (Method 3), resulted in poor proximal target coverage due to over-estimation of the densities of intervening tissues. Conclusion: 3D proton plans based on the CT obtained by averaging the 3D CTs comprising the 4D CT, and with the CT numbers in the tumor volume replaced by the corresponding MIP CT numbers, is an effective approach to achieve good tumor coverage and acceptable normal tissue sparing.
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TL;DR: In this article, the Bethe-Salpeter equation with recurrent scattering included in a frequency-dependent vertex function was used to renormalize the mean free path of the system.
Abstract: We study the dynamics of wave propagation in nominally diffusive samples by solving the Bethe-Salpeter equation with recurrent scattering included in a frequency-dependent vertex function, which renormalizes the mean free path of the system. We calculate the renormalized time-dependent diffusion coefficient, D(t), following pulsed excitation of the system. For cylindrical samples with reflecting side walls and open ends, we observe a crossover in dynamics in the transformation from a quasi-1D to a slab geometry implemented by varying the ratio of the radius, R, to the length, L. Immediately after the peak of the transmitted pulse, D(t) falls linearly with a nonuniversal slope that approaches an asymptotic value for R/L>>1. The value of D(t) extrapolated to t=0, depends only upon the dimensionless conductance g for R/L >1, where k is the wave vector and l is the bare mean free path.
Patent•
30 Sep 2005
TL;DR: In this paper, a set of extensionalmode microelectromechanical (MEMS) filters have been designed to achieve high resonant frequency, and high quality factors for radio frequency applications.
Abstract: A set of extensional-mode microelectromechanical (MEMS) filters has been designed to achieve high resonant frequency, and high quality factors for radio frequency applications. The filter designs comprising a membrane (16) including a plurality of spaced-apart periodic variations or holes (20) forming an array (18) that attenuates acoustic waves incident on the membrane (16) and having a wavelength greater than the spacing (S) between the periodic variations or holes (20), allow for easy coupling of individual resonators to form narrow band-pass filters for signal processing, and robust fabrication. The filter designs also eliminate energy dissipation into anchoring points and may be used for the general purpose of enhancing Q-factor in any extensional micro-mechanical devices.
TL;DR: In this paper, high-resolution transmission electron microscopy was used to measure the photoluminescence of ZnO quantum dots (QDs) embedded on silicon substrates by metal organic chemical vapor deposition at 350°C.
Abstract: Zinc oxide (ZnO) quantum dots (QDs) embedded films were fabricated on silicon substrates by metal organic chemical vapor deposition at 350°C. The QDs can be obtained in a matrix of amorphous ZnO films by introducing a large amount of precursors. The size of the QDs ranged from 3 to 12 nm, which was estimated by high-resolution transmission electron microscopy. The photoluminescence measured at 80 K showed that the emission of QDs embedded film ranged from 3.0 to 3.6 eV. The broad near-band-edge emission is due to the quantum confinement effect of the QDs. The quantum confinement effect of the QDs disappears after the post-growth annealing due to the ripening of QDs.