Evaluation of elastic modulus of cantilever beam by TA-ESPI

The paper proposes an evaluation technique for the elastic modulus of a cantilever beam by vibration analysis based on time average electronic speckle pattern interferometry (TA-ESPI) and Euler-Bernoulli equation. General approaches for the measurement of elastic modulus of a thin film are the Nano indentation test, Buldge test, Micro-tensile test, and so on. They each have strength and weakness in the preparation of the test specimen and the analysis of experimental results. ESPI is a type of laser speckle interferometry technique offering non-contact, high-resolution and whole-field measurement. The technique is a common measurement method for vibration mode visualization and surface displacement. Whole-field vibration mode shape (surface displacement distribution) at resonance frequency can be visualized by ESPI. And the maximum surface displacement distribution from ESPI can be used to find the resonance frequency for each vibration mode shape. And the elastic modules of a test material can be easily estimated from the measured resonance frequency and Euler-Bernoulli equation. The TA-ESPI vibration analysis technique can be used to find the elastic modulus of a material requiring simple preparation process and analysis.     

An Experimental Study of Mg Aggregation in AA5754 Alloys by Positron Annihilation Spectroscopy

Defects in an AA5754 （Al-3.0%Mg） alloy are investigated by coincidence Doppler broadening spectroscopy and positron lifetime spectroscopy. The results indicate enhancement of positron trapping by Mg atoms in this Al-Mg alloy after quenching treatment at 623K, which may be due to the formation of vacancy-Mg complexes or the aggregation of Mg near the vacancy sites. It is speculated that the aggregation of Mg atoms in the moderate temperature range is responsible for cracking in spot welding of AA5754 alloys.     

Shift-tolerance Property of Optical Security System using Phase-based Virtual Image

The shift-tolerance property of the encrypted image or the Fourier decrypting key in the Fourier space is proposed based on a phase-encoded virtual image. The encrypted data is obtained by the Fourier transform of the product of a phase-encoded virtual image to camouflage the original one and a random phase image. Therefore, even if unauthorized users analyze the encrypted image, they cannot reconstruct the required image. This virtual image protects the original one from being counterfeited and from unauthorized access. We demonstrate the robustness to data loss and shift of the encrypted data or the Fourier decrypting key in the proposed decryption technique using an interferometer.     

Quantum Dynamics of Systems Connected by a Canonical Transformation

Quantum Hamiltonian systems corresponding to classical systems related by a general canonical transformation are considered. The differential equation to find the unitary operator, which corresponds to the canonical transformation and connects quantum states of the original and transformed systems, is obtained. The propagator associated with their wave functions is found by the unitary operator. Quantum systems related by a linear canonical point transformation are analyzed. The results are tested by finding the wave functions of the under-, critical-, and over-damped harmonic oscillator from the wave functions of the harmonic oscillator, free-particle system, and negative harmonic potential system, using the unitary operator to connect them, respectively.     

Effects of Si-doped GaAs layer on optical properties of InAs quantum dots

We have investigated the optical properties of InAs self-assembled quantum dots (SAQDs) with the Si-doped GaAs barrier layer. Two types of samples are fabricated according to the position of the Si-doped GaAs layer. For type A samples the Si-doped GaAs layer is grown below the QDs, whereas for type B samples the Si-doped GaAs layer is grown above the QDs. For both types of samples the excited-state emissions caused by state filling are observed in photoluminescence (PL) spectra at high excitation power densities. The bandgap renormalization of QDs can be found from the shift of the PL peak energy. Particularly, for type A samples the Si atoms act as nucleation centers during the growth of InAs QDs on the Si-doped GaAs layer and affect the density and the size of the QDs. The Si-doped GaAs layer in type A samples has more effects on the properties of QDs, such as state filling and bandgap renormalization than those of type B samples.     

Bandgap engineering of self-assembled InAs quantum dots with a thin AlAs barrier

We investigate the effects of a thin AlAs layer with different position and thickness on the optical properties of InAs quantum dots (QDs) by using transmission electron microscopy and photoluminescence (PL). The energy level shift of InAs QD samples is observed by introducing the thin AlAs layer without any significant loss of the QD qualities. The emission peak from InAs QDs directly grown on the 4 monolayer (ML) AlAs layer is blueshifted from that of reference sample by 219 meV with a little increase in FWHM from 42–47 meV for ground state. In contrast, InAs QDs grown under the 4 ML AlAs layer have PL peak a little redshifted to lower energy by 17 meV. This result is related to the interdiffusion of Al atom at the InAs QDs caused by the annealing effect during growing of InAs QDs on AlAs layer.     

Optimization of in-vacuo template-stripped Pt surfaces via UHV STM

A recently demonstrated [1] in-vacuo template-stripping process is applied to the study of platinum films stripped from ultra-flat silicon-oxide surfaces. Template-stripped (TS) Pt surfaces, prepared with a range of post-deposition annealing times prior to being stripped from the templating surface in an ultra-high vacuum (UHV) environment, are examined by UHV scanning tunneling microscopy (STM). These studies reveal that without post-deposition annealing, TS Pt surfaces are largely made up of poorly-ordered, granular nanostructures undesirable for many applications. The post-deposition annealing treatments explored in the study result in the emergence and continuous growth of large smooth crystallites. Issues with crystallite orientation relative to the TS surface and artefacts arising as a result of the epoxy used in the template-stripping process are presented and discussed in relation to optimizing the template-stripping procedure for specific applications such as self-assembled monolayer (SAM) formation for molecular electronics. PACS 68.37.Ef; 68.47.De; 68.55.Jk; 81.05.Bx; 81.15.Ef