Manipulation of electronic property of epitaxial graphene on SiC substrate by Pb intercalation

Manipulating the electronic properties of graphene has been a subject of great interest since it can aid material design to extend the applications of graphene to many different areas. In this paper, we systematically investigate the effect of lead (Pb) intercalation on the structural and electronic properties of epitaxial graphene on the SiC(0001) substrate. We show that the band structure of Pb-intercalated few-layer graphene can be effectively tuned through changing intercalation conditions, such as coverage, location of Pb, and the initial number of graphene layers. Lead intercalation at the interface between the buffer layer (BL) and the SiC substrate decouples the BL from the substrate and transforms the BL into a p-doped graphene layer. We also show that Pb atoms tend to donate electrons to neighboring layers, leading to an n-doping graphene layer and a small gap in the Dirac cone under a sufficiently high Pb coverage. This paper provides useful guidance for manipulating the electronic properties of graphene layers on the SiC substrate

High-Performance and Flexible Metamaterial Wave Absorbers with Specific Bandwidths for the Microwave Device

In this paper, we proposed a high-performance electromagnetic-wave metamaterial absorber which can be used directly for 5G technology. The absorber exhibits a high performance in a tailored frequency range of 28 ± 1 GHz. At both transverse-electric and transverse-magnetic polarization, the absorption exceeds 99% when the electromagnetic wave is incident normally, and the absorption keeps being over 97% as the incident angle increases even to 45 degrees. The absorber is flexible, and it is very suitable for mass production because the production process is simple. In addition, the minimum dimension of the meta-structure is only 0.2 mm, and the cost is relatively low. Similarly, another high-performance metamaterial absorber with a tailored bandwidth at the center frequency of 77 GHz, which is relevant to self-driving cars, was also prepared by a minimal adjustment to the original structure

Measuring the Wall Thickness of a Trailing Arm Using Ultrasonic Measurement Model

Trailing arms are widely used in the automobiles’ suspension system, and effective detection of their wall thickness is essential to ensure their mechanical properties and to evaluate the casting process. In this work, an ultrasonic measurement model (UMM) is firstly established with consideration of the curvature and thickness of the trailing arm, then the UMM is introduced to predict the theoretical ultrasonic waveforms with different hypothetical thicknesses of the trailing arm. Next, the experimental ultrasonic waveforms are collected and matched with the predicted theoretical waveforms by using the correlation matching algorithm. The hypothetical thickness with the best match is regarded as the wall thickness of the trailing arm. Finally, an automatic ultrasonic experiment was conducted on a trailing arm with a 5-degrees of freedom (DOF) manipulator, in which the ultrasonic beam can radiate into a trailing arm at normal incidence. The results are compared with those determined by the micrometer and microscope, showing that their relative errors are controlled within 0.08 mm, which reveals the effectiveness of the present method. The method can also work for wall thickness measurements of curved components with CAD models

Flexible Metamaterial Absorber with Tailored Bandwidth and High Absorption Performance

Different from previous works which have focused on broadening the bandwidth, we propose an electromagnetic absorber with a medium and tailored bandwidth absorption, which avoids the unnecessary absorption caused by the too-wide bandwidth. Nevertheless, absorption is extremely high to be more than 99% and 97% for the normal and even oblique (45°) incidence, respectively, in a tailored frequency range of 5.8 ± 0.25 GHz even for both TE and TM polarization. This means the absorber is insensitive to the polarization of incident electromagnetic wave. Furthermore, it is flexible, since the main portion of sample is soft and flexible polyimide. The same properties are also realized in a range of 10 ± 0.5 GHz through adjusting the parameters of structure. The center frequencies of 5.8 and 10 GHz are very useful in our daily life, and the cost of absorber is relative low. Therefore, we believe the absorber can be used in many practical fields such as vehicle high-pass applications and radars

Flexible Metamaterial Absorber with Tailored Bandwidth and High Absorption Performance

Different from previous works which have focused on broadening the bandwidth, we propose an electromagnetic absorber with a medium and tailored bandwidth absorption, which avoids the unnecessary absorption caused by the too-wide bandwidth. Nevertheless, absorption is extremely high to be more than 99% and 97% for the normal and even oblique (45°) incidence, respectively, in a tailored frequency range of 5.8 ± 0.25 GHz even for both TE and TM polarization. This means the absorber is insensitive to the polarization of incident electromagnetic wave. Furthermore, it is flexible, since the main portion of sample is soft and flexible polyimide. The same properties are also realized in a range of 10 ± 0.5 GHz through adjusting the parameters of structure. The center frequencies of 5.8 and 10 GHz are very useful in our daily life, and the cost of absorber is relative low. Therefore, we believe the absorber can be used in many practical fields such as vehicle high-pass applications and radars

Advances in condensed matter optics

This book describes some of the more recent progresses and developmentsin the study of condensed matter optics in both theoretic and experimental fields.It will help readers, especially graduate students and scientists who are studying and working in the nano-photonic field, to understand more deeply the characteristics of light waves propagated in nano-structure-based materials with potential applications in the future

Method for Analyzing the Measurement Error with Respect to Azimuth and Incident Angle for the Rotating Polarizer Analyzer Ellipsometer

We proposed a method to study the effects of azimuth and the incident angle on the accuracy and stability of rotating polarizer analyzer ellipsometer (RPAE) with bulk Au. The dielectric function was obtained at various incident angles in a range of 55°–80° and analyzed with the spectrum of the principal angle. The initial orientations of rotating polarizing elements were deviated by a series of angles to act as the azimuthal errors in various modes. The spectroscopic measurements were performed in a wavelength range of 300–800 nm with an interval of 10 nm. The repeatedly-measured ellipsometric parameters and determined dielectric constants were recorded monochromatically at wavelengths of 350, 550, and 750 nm. The mean absolute relative error was employed to evaluate quantitatively the performance of instrument. Apart from the RPAE, the experimental error analysis implemented in this work is also applicable to other rotating element ellipsometers