With the deep research of measurement for microscopic or nanometer level scale at present the concept of Critical Dimension(CD) is pointed out in many papers[1,4,], they always include some analyses of measuring uncertainty for current technology of measurement, but our new idea or definition for geometrical action scale (GAS) is the limited scale or uncertainty of measurement in microscope that we can approach to for the most advanced method, technology, set-up or instrument, for example: The modern interferometer, SPM[5] and other various scattering experiments using the beam of microscopic particles. It would be found that the research included fundamentals for microscopic particle geometric scale is not easy to explore, some reasons perhaps are affected by which the classical quantum mechanics study of matter usually start from energy or energy level not from geometrical scale and by the Heisenberg relation of measuring uncertainty. Our work just wants to research on these fundamentals in physics for microscopic particles geometric scale. At first, a new physical quantity relative to microscopic particle geometric scale is directly suggested in this paper, it also may be deduced from the completeness of units system or dimension system refer to optics principles or quantum optics principles. We find that the wavelength of Louis de Broglie matter wave is either the length dimension or relative to the geometric scale of microscopic particles, and we define it as the geometrical action scale (GAS) of microscopic particles. The significance of the geometrical scale of microscopic particles or GAS in physics is discussed.
The dynamics of carriers/excitons in as grown and annealed ZnO epilayers at room-temperature under high excitation densities were monitored by pump-probe(4.65/3.1 eV) differential reflectance transients on a time scale equal to 100 ps. The ΔR buildup showed a density-independent time delay of about 1.45 ps relative to the pump pulse, indicative of hot phonon effects, i.e., LO-phonon bottleneck, common to the as grown and annealed ZnO epilayers. Both appeared an initial fast ΔR decay with a time constant of about 20-25 ps due to rapid defect trapping. After the fast decay, the ΔR transient of the as grown ZnO became of sign reversal and turned to an induced absorption signal from defect levels with a decay time of several hundred picoseconds weakly dependent on excitation intensities. For the annealed ZnO, no change over in sign was observed on the slowly recovering component of ΔR, of which, in particular, the decay time was found to linearly depend upon carrier density. This finding, as confirmed by photoluminescence measurements, was attributed to a bimolecular recombination in terms of an exciton-exciton scattering in ZnO. These observations suggest that this unique pump-probe technique can provide a useful tool for understanding the defect physics of semiconducting materials.
Dense and crack-free SBN thin films with the preferred c-axis orientation were successfully fabricated by the sol-gel method on Si(100) substrates with a MgO buffer layer. It was found that introducing the MgO buffer layer could effectively promote the formation of TTB SBN phase from SN and BN phases at lower temperature. Effects of annealing temperature and thickness of MgO buffer layer on the structural and morphological properties of SBN thin films were investigated. The SBN film with MgO buffer layer showed excellent epitaxy and densely packed grain morphology. The capacitance-voltage (C-V) properties of SBN films deposited on silicon substrates were found completely different from those of the films deposited on MgO-buffered silicon substrates, the C-V curves of SBN/Si films and SBN/MgO/Si films represent typical shapes of asymmetric and butterfly, respectively, indicating the improvement of the electrical properties and ferroelectric properties of the SBN films by introducing the MgO buffer layer.
Highly oriented ferroelectric strontium barium niobate (Sr0.6Ba0.4Nb2O6) thin films were prepared on P-type Si(100) substrate by the Sol-Gel process. The XRD patterns of the SBN films show that SBN film prepared by using NbCl5, KOH as raw materials performed a highly c-axis preferred orientation perpendicular to the Si substrate, better than films that was prepared using Nb(OC2H5)5 as starting agents. It may be duo to the existence of the potassium ion that not be filtered out completely during the preparation of the niobium alkoxide. The characteristics of D-F and C-V curves were obtained for SBN/Si film. The film exhibits high dielectric constant. In order to investigate ferroelectric characteristics further, the P-E loops of the SBN/Pt/Si were also measured. The films show better optical properties, transmittance of Sr0.6Ba0.4Nb2O6 films on MgO(001) and SiO2 substrates was more than 60% at the range from 450 to 850nm, refractive index was measured to be 2.14 and 2.12 on the MgO and SiO2 substrate at 633nm respectively.
Room-temperature spectral and temporal behaviors of UV and visible emissions in ZnO epilayers grown onto (100) silicon substrates have been investigated by means of time-integrated and time-resolved photoluminescence(TIPL & TRPL). The PL lifetimes as short as 25-50 ps for the excitonic UV lines peaked at ~380 nm were found, indicative of ultrafast trapping of excitons by defects states inside the band gap. Compared to its as-grown precursor, the ZnO epilayer subjected to postgrowth thermal annealing in air showed enhanced intensities of both UV as well green emissions by nearly the same factor of ~3.1, in accompany with complete disappearance of the impurity luminescence peaked at 2.83 eV. More importantly, the green luminescence in the post-annealed ZnO was observed to decay as hyperbolic t-1 and logarithmically shift its peak emission toward higher energies with increased excitation intensity, in excellent agreement with the tunnel-assisted donor-acceptor pair(DAP) recombination model. The possible mechanism of compensation between intrinsic impurities was also discussed.
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