We investigated the low temperature performance of CoFeB/MgO-based perpendicular magnetic tunnel junctions (pMTJs) by characterizing their quasi-static switching voltage, high speed pulse write error rate, and endurance down to 9 K. pMTJ devices exhibited high magnetoresistance (>120%) and reliable (error rate < 10(-4)) bi-directional switching with 2-200 ns voltage pulses. The endurance of the devices at 9 K surpassed that at 300 K by three orders of magnitude under the same write conditions, functioning for more than 10(12) cycles with 10 ns write pulses. The switching voltage at 9 K was observed to increase by 33% to 93%, depending on the pulse duration, compared to that at 350 K. Ferromagnetic resonance and magnetization measurements on blanket pMTJ film stacks suggest that the increased switching voltage is associated with an increase in the energy barrier of the free layer with decreasing temperature. Our work demonstrates that CoFeB/MgO-based pMTJs have great potential to enable cryogenic magnetic random access memory and that their exchange stiffness, magnetization, and effective magnetic anisotropy can be further optimized to lower operating power and improve endurance.

Silicon-on-insulator (SOI) is the most suitable platform for silicon photonics applications owing to its unique structure and excellent compatibility. To satisfy the requirement of uniformity, HCl etching process is developed to smooth the surface of top silicon layer in this paper. The top silicon mean thickness is thinned down to 220 nm; the corresponding root mean square roughness is as low as 0.165 nm after the etching process, which is comparable to chemical mechanical polishing (CMP) process. Furthermore, HCl etching process shows great repeatability of thickness range and removal amount. The within wafer thickness range can be controlled below 30 angstrom and the removal amount can be controlled within +/- 4.5 angstrom, which is far better than conventional CMP process.

设计了基于AD5933的无创皮肤阻抗测量系统,用来评估皮肤渗透能力,提高经皮给药、提取组织液目标物的效率.系统利用二电极比例法,并采用时钟频率切换、量程自动切换和软件校准补偿等技术,实现了对低频皮肤阻抗的测量.基于电穿孔法进行促渗透处理前后的皮肤对系统进行了阻抗测量实验验证.结果表明:该系统可用于对皮肤渗透性的表征,可给人体生理生化检测相关的可穿戴设备参数调节提供依据.

The doped polycrystalline silicon (poly-Si) is used to investigate the effects of boron on non-linear properties of trap-rich silicon-on-insulator (TR-SOI) substrates. A dip at poly-Si/Si interface in spreading resistance profiles (SRP) is found and attributed to certain combinations of the poly-Si layer and the substrate dopant levels. A multilayered SRP model is employed to explain the SRP characteristics of the poly-Si films. The non-linear performance of TR-SOI is also studied using 50 Omega coplanar waveguide (CPW) lines. The results show little impact to the second harmonic distortion (HD2) up to 1 x 10(15) cm(-3) boron concentration in the poly-Si layer. At boron doping levels of above 5 x 10(15 )cm(-3) measurable deteriorations of HD2 are detected and significantly worse when boron doping level in poly-Si reaches 1 x 10(17 )cm(-3), presumably the traps in grain boundaries of poly-Si layer are filled by doping charges.

Electrical properties of boron lightly doped trap-rich layers of trap-rich high resistivity silicon-on-insulator (trap-rich HR-SOI) substrates are investigated. Secondary Ion Mass Spectroscopy (SIMS) is used to measure boron distribution. Resistivity profiles are studied by means of Spreading-resistance profiling (SRP). Moreover, radio frequency (RF) performance of the trap-rich HR-SOI substrates is evaluated using coplanar waveguide (CPW) lines. It is found that RF losses and harmonic distortions keep unchanged when boron concentration of the trap-rich layer is lower than 5 x 10(14) cm(-3). It is suggested that the trap-rich layer can still effectively restrain the parasitic surface conductance (PSC) effect. (c) 2018 The Electrochemical Society.

Skin penetration is related to efficiencies of drug delivery or ISF extraction. Normally, the macro-electrode is employed in skin permeability promotion and evaluation, which has the disadvantages of easily causing skin damage when using electroporation or reverse iontophoresis by alone; furthermore, it has large measurement error, low sensitivity, and difficulty in integration. To resolve these issues, this paper presents a flexible interdigital microelectrode for evaluating skin penetration by sensing impedance and a method of synergistical combination of electroporation and reverse iontophoresis to promote skin penetration. First, a flexible interdigital microelectrode was designed with a minimal configuration circuit of electroporation and reverse iontophoresis for future wearable application. Due to the variation of the skin impedance correlated with many factors, relative changes of it were recorded at the end of supply, different voltage, or constant current, times, and duration. It is found that the better results can be obtained by using electroporation for 5 min then reverse iontophoresis for 12 min. By synergistically using electroporation and reverse iontophoresis, the penetration of skin is promoted. The results tested in vivo suggest that the developed microelectrode can be applied to evaluate and promote the skin penetration and the designed method promises to leave the skin without damage. The electrode and the method may be beneficial for designing noninvasive glucose sensors.

Crystal morphologies and resistivity of polysilicon trap-rich layers of two generation trap-rich silicon-on-insulator (TR-SOI) substrates are studied. It is found that the resistivity of the trap-rich layer of generation 2 (TR-G2) is higher than that of generation 1 (TR-G1), although the crystal morphologies of the trap rich layers are the same. In addition, the rf performance of two-generation TR-SOI substrates is investigated by coplanar waveguide lines and inductors. The results show that both the rf loss and the second harmonic distortion of TR-G2 are smaller than those of TR-G1. These results can be attributed to the higher resistivity values of both the trap-rich layer and the high-resistivity silicon (HR-Si) substrate of TR-G2. Moreover, the rf performance of the TR-SOI substrate with thicker buried oxide is slightly better. The second harmonics of various TR-SOI substrates are simulated and evaluated with the harmonic quality factor model as well. It can be predicted that the TR-SOI substrate will see further improvement in rf performance if the resistivities of both the trap-rich layer and HR-Si substrate increase.

Traditionally, skin permeability evaluation, which is realized by impedance detected at a certain frequency based on macro electrodes, has the disadvantages of large measurement error, low sensitivity and difficulty in integration. In order to resolve this problem, a flexible non-symmetric interdigital microsensor is designed by analyzing the layered structure of skin and the relationship between skin permeability and impedance of Stratum Corneum(SC). The impedance of SC is measured and analyzed based on the RCW-layered impedance model. It is illustrated that the impedance magnitude vertical bar Z(msd)(100)vertical bar of microsensor output and model fitting parameters R-sc can be used as the important indicators to evaluate skin permeability. It is proved that the developed sensor can be applied to distinguishing the different individuals' skin permeability, and it strongly supports the adjustment of wearable devices related to human physiological and biochemical detection.

Due to advances in telemedicine, mobile medical care, wearable health monitoring, and electronic skin, great efforts have been directed to non-invasive monitoring and treatment of disease. These processes generally involve disease detection from interstitial fluid (ISF) instead of blood, and transdermal drug delivery. However, the quantitative extraction of ISF and the level of drug absorption are greatly affected by the individual's skin permeability, which is closely related to the properties of the stratum corneum (SC). Therefore, measurement of SC impedance has been proposed as an appropriate way for assessing individual skin differences. In order to figure out the current status and research direction of human SC impedance detection, investigations regarding skin impedance measurement have been reviewed in this paper. Future directions are concluded after a review of impedance models, electrodes, measurement methods and systems, and their applications in treatment. It is believed that a well-matched skin impedance model and measurement method will be established for clinical and point-of care applications in the near future.

High-resistivity silicon-on-insulator (HR-SOI) and trap-rich high-resistivity silicon-on-insulator (TR-SOI) substrates have been widely adopted for high-performance rf integrated circuits. Radio-frequency loss and non-linearity characteristics are measured from coplanar waveguide (CPW) transmission lines fabricated on HR-SOI and TR-SOI substrates. The patterned insulator structure is introduced to reduce loss and non-linearity characteristics. A metal-oxide-semiconductor (MOS) CPW circuit model is established to expound the mechanism of reducing the parasitic surface conductance (PSC) effect by combining the semiconductor characteristic analysis (pseudo-MOS and C–V test). The rf performance of the CPW transmission lines under dc bias supply is also compared. The TR-SOI substrate with the patterned oxide structure sample has the minimum rf loss (<0.2 dB/mm up to 10 GHz), the best non-linearity performance, and reductions of 4 dB and 10 dB are compared with the state-of-the-art TR-SOI sample's, HD2 and HD3, respectively. It shows the potential application for integrating the two schemes to further suppress the PSC effect.