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In this paper, we present ultra-high quality factor ( ${Q}$ ) SAW resonators fabricated on aluminum gallium nitride on gallium nitride on silicon (AlGaN/GaN/Si) heterostructures with ${Q}$ exceeding 6000 at room temperature. We characterize their temperature response in a broad range of temperature (−196°C to 500°C or 77 K to 773 K). The effect of doping on the ${Q}$ and temperature coefficient of frequency (TCF) of the GaN-based SAW resonators is analyzed, for the first time, using un-intentionally doped GaN (UID-GaN), carbon doped GaN (C-doped), and Si doped GaN. The ${Q}$ value for UID-GaN and C-doped GaN is similar and decreases from 2000 to 1000 as the temperature is increased from 77 K to 773 K. The ${Q}$ value of Si-doped GaN is higher than UID and C-doped GaN by a factor of 3 (6622 at 77 K) and decreases with increase of temperature. This value of ${Q}$ at 1.8 GHz is the highest reported amongst aluminum nitride (AlN) or GaN-based SAW resonators. For extreme high temperatures (≥573 K) the TCF value is half the TCF value of UID and C-doped GaN, which shows the possibility of engineering the TCF by tuning the doping concentration. For low temperatures (≤150 K) C-doped and UID-GaN show a turn over point in TCF curve which shows their promise for cold clocks. [2020-0163]

This paper reports on the investigation of anomalous low quality factors ( ${Q}\text{s}$ ) in AlN thin film-based length extensional (LE)-mode resonators using finite element method (FEM), analytical modeling, and experimental techniques. Different heterostructures of LE resonators having Al/AlN/Si, Al/AlN, AlN/Si, and Si are designed and fabricated using standard MEMS processes. Experimental ${Q}\text{s}$ along with resonances are obtained using electrical and optical readout and are compared with the modeled and analytically obtained ${Q}\text{s}$ . The results show that the thermoelastic damping (TED) in metal electrode, anchor loss, and charge redistribution loss are not the dominant loss mechanisms. With the help of Mason’s network modeling, we investigated the dielectric loss, which is also observed to be negligible for these resonators. An internal mechanical loss, originating from the columnar growth of AlN and observed using Mason’s model, is proved to be the dominant loss mechanism. This observation is confirmed and reinforced by the COMOSL’s FEM analysis of TED in AlN, having columnar growth effect and by experimental results. [2018-0258]

Silicon carbide (SiC) has been extensively investigated in the last decade, specifically for applications in harsh environments. However, most SiC sensors require an external power supply, which cannot operate at high temperatures. This letter develops a new sensing technology in a SiC platform based on near field communication to eliminate the requirement for wired power sources. The 3C-SiC temperature sensors were fabricated from a SiC-on-insulator substrate formed by anodic bonding. The sensors functioned based on the thermoresistance of the SiC films with the high TCR of −13 000 ppm/K at 300 K and −3 000 ppm/K at 600 K. The resistance change of the sensors was wirelessly measured using a reading coil placed outside of the heating chamber, showing a significant resonant-frequency-shift (−400 ppm/K at 600 K) of the coupling impedance under temperature variation. The proposed technique is promising for the development of wireless wide-band-gap sensors used in extreme conditions.

We demonstrate coupled bulk and surface acoustic wave (BAW/SAW) resonators with significantly improved coupling efficiency as compared to SAW only devices. Two sets of stacks are investigated: one uses a thin film piezoelectric material with a bottom electrode on GaN substrate (i.e., AlN/Mo/GaN) and another includes a piezoelectric thin film with bottom metal on a Si substrate (i.e., AlN/Mo/Si). A vibrating BAW transducer induces a SAW in the substrate and between two sets of interdigitated transducers improving the coupling efficiency by a factor of ${\geq }\, \mathsf {8}{x}$ as compared to the conventional SAW. The performance of the coupled BAW/SAW resonators using each of the Si and GaN substrates is compared using FEM analysis. By using FEM, coupling efficiency of the hybrid BAW/SAW with AlN/Mo/Si stack is 2.4%, whereas it is 3.2% for the SAW using AlN/Mo/GaN stack.

This letter reports the first results on a new generation of anti-symmetric lamb-wave devices using a simple solidly mounted platform of AlN/Mo/Si and operating at very-high-to-super-high frequency range. AlN/Mo/Si-based solidly mounted resonators (SMRs) with sub-micrometer interdigitated transducers were fabricated using the electron beam lithography and liftoff process. Plasma etching was used to etch vias in ground pads to get access to the bottom electrode for grounding. By comparing the floating, grounded, and no bottom electrode device performances, it has been observed that the presented SMR design with grounded bottom electrode results in enhancement of the coupling efficiency by 500% compared with conventional SAW devices. In addition, these devices are more mechanically robust and can be monolithically integrated with a CMOS platform without requiring complex packaging processes compared with conventional released lamb-wave resonators.

This paper reports, for the first time, on the engineering of silicon-doped gallium nitride (GaN) based surface acoustic wave (SAW) devices for ultra-stable clocks with frequency stability of better than 20 ppb/°C over the temperature range of −196°C to 27°C. Such exceptional temperature stability of GaN acoustic resonators at low temperatures prove their applicability for emerging space explorations to planetary bodies with extreme low temperature swings. In this work, we have exploited silicon doping of GaN to enable further stabilization of the SAW resonator by self-ovenization using the Joule heating generated from a DC current that is passed through the resonator body. Furthermore, we demonstrate the effect of doping on the temperature coefficient of frequency (TCF) of GaN SAW resonators.

With its unprecedented properties over conventional rigid platforms, flexible electronics have been a significant research topic in the last decade, offering a broad range of applications from bendable display, flexible solar-energy systems, to soft implantable-devices for health monitoring. Flexible electronics for harsh and hazardous environments have also been extensively investigated. In particular, devices with stretchability and bend-ability as well as tolerance to extreme and toxic operating conditions are imperative. This work presents silicon carbide grown on silicon and then transferred onto polyimide substrate as a new platform for flexible sensors for hostile environments. Combining the excellent electrical properties of SiC and high temperature tolerance of polyimide, we demonstrated for the first time a flexible SiC sensors that can work above 400 °C. This new sensing platform opens exciting opportunities toward flexible sensing applications in hazardous environments.

The pseudo-Hall effect in n-type single crystal 3C-SiC(1 0 0) with low carrier concentration has been investigated. Low pressure chemical vapor deposition was used to grow the single crystal n-type 3C-SiC(1 0 0) and Hall devices were fabricated by photolithography and dry etch processes. A large pseudo-Hall effect was observed in the grown thin films which showed a strong dependence on the crystallographic orientation. N-type 3C-SiC(1 0 0) with low carrier concentration shows a completely different behavior of pseudo-Hall measurements as compared to the p-type 3C-SiC(1 0 0). Contrary to p-type, the effect is maximum along [1 0 0] crystallographic orientation and minimum along [1 1 0] orientation. Moreover, the observed pseudo-Hall effect is 50 larger than p-type with higher carrier concentration grown by the same process which makes n-type 3C-SiC(1 0 0) with low carrier concentration more suitable material for designing highly sensitive micro-mechanical sensors.

Microelectromechanical systems sensors have been intensively developed utilizing various physical concepts, such as piezoresistive, piezoelectric, and thermoresistive effects. Among these sensing concepts, the thermoresistive effect is of interest for a wide range of thermal sensors and devices, thanks to its simplicity in implementation and high sensitivity. The effect of temperature on the electrical resistance of some metals and semiconductors has been thoroughly investigated, leading to the significant growth and successful demonstration of thermal-based sensors, such as temperature sensors, convective accelerometers and gyroscopes, and thermal flow sensors. In this paper, we review the fundamentals of the thermoresistive effect in metals and semiconductors. We also discuss the influence of design and fabrication parameters on the thermoresistive sensitivity. This paper includes several desirable features of thermoresistive sensors and recent developments in these sensors are summarized. This review provides insights into how it is affected by various parameters, and useful guidance for industrial designers in terms of high sensitivity and linearity and fast response. [2017-0022]

Dynamics of spin ordering in the manganite Nd0.5Ca0.5MnO3 have been investigated in this paper. It was observed that the complex mixed magnetic ordering in pellets is comprised of antiferromagnetic ordering at 160 K (TN) and complete charge ordering at 250 K (TCO). Under ac field, appearance of unstable ferromagnetic correlations is observed above TCO, which is badly frustrated due to strong spin disorder induced by Jahn Teller distortions. Impedance measurements reveal the spin glass like scenario, suppressing the strong antiferromagnetic and charge ordering states below TN.

Silicon carbide on insulator is a promising platform for electronic devices at high temperature as well as for opto-electrical applications. Utilizing the chemical inertness of SiC, this work presents a novel technique to form cubic-silicon carbide (3C-SiC) on silicon dioxide (SiO2) by using silicon wet-thermal-oxidation. Experimental data confirmed that SiO2 was successfully formed underneath of 300 nm width SiC nanowires, while the properties of SiC was almost unaffected during the oxidation process. This simple technique will open the pathway to the development of SiCOI (SiC on insulator) based electrical and optical applications.

This article reports the first results on stress induced pseudo-Hall effect in single crystal n-type 3C-SiC(100) grown by LPCVD process. After the growth process, Hall devices were fabricated by standard photolithography and dry etching processes. The bending beam method was employed to study the stress induced changes in the electrical response of the fabricated Hall devices. It has been observed that when stress is applied to the 3C-SiC(100) Hall devices, the offset voltage of the Hall devices varies linearly with the applied compressive and tensile stresses which is called, the pseudo-Hall effect. The variation of the offset voltage of these Hall devices is also proportional to the applied input current. This variation of the offset voltage with the applied compressive and tensile stresses shows that single crystal n-type 3C-SiC(100) can be used for stress sensing applications.

Position-sensitive detectors (PSDs) utilising the lateral photovoltaic effect (LPE) are actively being explored to achieve precise optical alignments for applications such as surface profiling, motion tracking, and robotics. However, the development of ultrasensitive PSDs has faced great challenges due to the limitation of conventional architectures and nature of photosensitive materials. Herein, we propose a novel PSD nanoarchitecture based on horizontally-aligned double 3C-SiC/Si heterostructures. The unique device configuration allows the effective generation, separation, and migration of photogenerated carriers to one electrode, while eliminating the diffusion of these charge carriers to the other, enabling a large gradient of charge or lateral photovoltage between the electrodes. The PSD showed an ultra-high sensitivity of 1780 mV/mm at an illumination intensity of 5.6 W/cm2 (980 nm) at zero bias conditions (i.e., self-powered), which is approximately 620% more sensitive than that of standard-type 3C-SiC/Si PSD and over 250% larger than the best position-sensitivity detector reported to date. The innovative nanoarchitecture demonstrated in this work holds promises for developing industry-compatible ultra-sensitive self-powered position-sensitive detectors.

This letter reports on the piezoresistive effect of top–down fabricated 3C-SiC nanowires (NWs). Focused ion beam was utilized to create p-type 3C-SiC NWs from a 3C-SiC thin film with a carrier concentration of $5 \times 10^{18}$ cm $^{-3}$ epitaxially grown on a Si substrate. The as-fabricated NWs were then subjected to tensile strains varying from 0 to 280 $\mu \varepsilon $ . Experimental data showed that the p-type 3C-SiC NWs possess a large gauge factor of 35, which is at least one order of magnitude larger than that of other hard materials, such as carbon nanotubes and graphene. This large gauge factor and the linear relationship between the relative resistance change and the applied strain in the SiC NWs indicate their potential for nanoelectromechanical systems sensing applications.

In this work, we demonstrate highly thermosensitive silicon nanowires (SiNWs) for thermal-sensing applications. Crystalline Si was amorphized by Focused Ion Beam in the fabrication process of the SiNWs, and subsequently recrystallized by a thermal annealing process to improve their electrical conductivity. A temperature coefficient of resistance (TCR) from −8000 ppm/K to −12,000 ppm/K was measured for the SiNWs. This large negative TCR is attributed to the boundary potential barrier of 110 meV between silicon crystallites in the poly crystalline SiNWs.

This article reports the first results on piezo-Hall effect in single crystal p-type 3C–SiC(100) Hall devices. Single crystal p-type 3C–SiC(100) was grown by low pressure chemical vapor deposition, and Hall devices were fabricated using the conventional photolithography and dry etching processes. An experimental setup capable of applying stress during Hall-effect measurements was designed to measure the piezo-Hall effect. The piezo-Hall effect is quantified by directly observing the variation in magnetic field sensitivity of the Hall devices upon an applied stress. The piezo-Hall coefficient P12 characterized by these measurements is found to be 6.4 × 10−11 Pa−1.

Flexible and stretchable electronics have a wide variety of wearable applications in portable sensors, flexible electrodes/heaters, flexible circuits and stretchable displays. Spinnable carbon nanotubes (CNTs) constructed on flexible substrates are potential materials for wearable sensing applications owing to their high thermal and electrical conductivity, low mass density and excellent mechanical properties. Here, we demonstrate a wearable thermal flow sensor for healthcare using lightweight, high strength, flexible CNT yarns as hotwires, pencil graphite as electrodes, and lightweight, recyclable and biodegradable paper as flexible substrates, without using any toxic chemicals. The CNT-based sensor which could be utilized to monitor respiratory diseases is comfortably affixed to human skin and detects real-time human respiration. We also successfully demonstrate the temperature detecting functionality integrated in the same sensor, which can measure body temperature using a non-contact mode. The results indicate that the CNT yarn can be used to develop a wide range of environment-friendly, low-cost and lightweight paper-based flexible devices for wearable applications in temperature and respiratory monitoring, and personal healthcare.

Flexible and multifunctional electronic devices have been proven to show potential for various applications including human-motion detection and wearable thermal therapy. The key advantages of these systems are (1) highly stable, sensitive and fast-response devices, (2) fabrication of macroscale devices on flexible substrates, and (3) integrated (lab-on-chip) and multifunctional devices. However, their fabrication commonly requires toxic solvents, as well as time-consuming and complex processes. Here, we demonstrate the low-cost, rapid-prototyping and user-friendly fabrication of flexible transducers using recyclable, water-resistant poly(vinyl chloride) films as a substrate, and ubiquitously available pencil graphite as a functional layer without using any toxic solvents or additional catalysts. The flexible heaters showed good characteristics such as fast thermal response, good thermostability (low temperature coefficient of resistance) and low power consumption. The heaters with their capability of perceiving human motion were shown to be effective. The proof of concept of other functional devices such as vibration-based droplet sensors and drag-force air flow sensors was also demonstrated. Results from this study indicate that a wide range of electronic devices fabricated from the environmental-friendly material by this simple and user-friendly approach could be utilized for cost-effective, flexible and low power consuming thermal therapy, health monitoring systems and other real-time monitoring devices without using any toxic chemicals or advanced processes.

This paper presents for the first time the effect of strain on the electrical conductivity of p-type single crystalline 3C–SiC grown on a Si (111) substrate. 3C–SiC thin film was epitaxially formed on a Si (111) substrate using the low pressure chemical vapor deposition process. The piezoresistive effect of the grown film was investigated using the bending beam method. The average longitudinal gauge factor of the p-type single crystalline 3C–SiC was found to be around 11 and isotropic in the (111) plane. This gauge factor is 3 times smaller than that in a p-type 3C–SiC (100) plane. This reduction of the gauge factor was attributed to the high density of defects in the grown 3C–SiC (111) film. Nevertheless, the gauge factor of the p-type 3C–SiC (111) film is still approximately 5 times higher than that in most metals, indicating its potential for niche mechanical sensing applications.

This letter reports on cubic silicon carbide (3C–SiC) transferred on a glass substrate as an ideal platform for thermoresistive sensors which can be used for in situ temperature measurement during optical analysis. The transfer of SiC onto an insulating substrate prevents current leakage through the SiC/Si junction, which is significantly influenced by visible light. Experimental data shows that the 3C–SiC on glass based sensor possesses a large temperature coefficient of resistance (TCR) of up to −7508 ppm K−1, which is about 10 times larger than that of highly doped Si. Moreover, the 3C–SiC based temperature sensor also outperforms low doped Si in terms of stability against visible light. These results indicate that 3C–SiC on glass could be a good thermoresistive sensor to measure the temperature of cells during optical investigations.

Harvesting sustainable energy resources from surrounding environments to power small electronic devices and systems has attracted massive research attention. Herein, we develop a novel technology to harvest light energy to self-power and simultaneously sense mechanical acceleration in a monolithic structure. When the photonic gate is illuminated the operation mode of the device changes from conventional mode to light harvesting and self-powered operation. The light illumination provides a gradient of majority carrier concentration on the top semiconductor layer, generating a lateral photovoltage, which is the output voltage of the sensor. Under acceleration, the mechanical inertial force induces stress in the sensor material leading to the change of mobility of the charge carriers, which shifts their diffusion rate, and hence changes the gradient of the majority carriers and the lateral photovoltage. The sensitivity at 480 lx light illumination was measured to be 107 μ V / g , while it was approximately 30 μ V / g under the ambient light illumination without any electrical power source. In addition, the acceleration sensitivity is tunable by controlling parameters of the photonic gate such as light power, light spot position and light wavelength. The integration of sensing and powering functions into a monolithic platform proposed in this work eliminates the requirement of external power sources and offers potential solutions for wireless, independent, remote, and battery-free sensing devices and systems.

Semiconductor nanowires are widely considered as the building blocks that revolutionized many areas of nanosciences and nanotechnologies. The unique features in nanowires, including high electron transport, excellent mechanical robustness, large surface area, and capability to engineer their intrinsic properties, enable new classes of nanoelectromechanical systems (NEMS). Wide bandgap (WBG) semiconductors in the form of nanowires are a hot spot of research owing to the tremendous possibilities in NEMS, particularly for environmental monitoring and energy harvesting. This article presents a comprehensive overview of the recent progress on the growth, properties and applications of silicon carbide (SiC), group III‐nitrides, and diamond nanowires as the materials of choice for NEMS. It begins with a snapshot on material developments and fabrication technologies, covering both bottom‐up and top‐down approaches. A discussion on the mechanical, electrical, optical, and thermal properties is provided detailing the fundamental physics of WBG nanowires along with their potential for NEMS. A series of sensing and electronic devices particularly for environmental monitoring is reviewed, which further extend the capability in industrial applications. The article concludes with the merits and shortcomings of environmental monitoring applications based on these classes of nanowires, providing a roadmap for future development in this fast‐emerging research field., Wide bandgap semiconductor nanowires with unique properties and advanced fabrication/integration technologies set a new class of nanosensing and electronic applications. Implementation of these smart devices such as gas sensors, photodetectors, wearable devices, strain sensors, and energy harvesters into environmental monitoring systems offers promising solutions for critical environmental challenges.

Improving and optimizing the processes for transfer printing have the potential to further enhance capabilities in heterogeneous integration of various sensing materials on unconventional substrates for implantable and stretchable electronic devices in biosensing, diagnostics, and therapeutic applications. An advanced transfer printing method based on sacrificial layer engineering for silicon carbide materials in stretchable electronic devices is presented here. In contrast to the typical processes where defined anchor structures are required for the transfer step, the use of a sacrificial layer offers enhances versatility in releasing complex microstructures from rigid donor substrates to flexible receiver platforms. The sacrificial layer also minimizes twisting and wrinkling issues that may occur in free‐standing microstructures, thereby facilitating printing onto flat polymer surfaces (e.g., polydimethylsiloxane). The experimental results demonstrate that transferred SiC microstructures exhibit good stretchability, stable electrical properties, excellent biocompatibility, as well as promising sensing‐functions associated with a high level of structural perfection, without any cracks or tears. This transfer printing method can be applied to other classes of wide bandgap semiconductors, particularly group III‐nitrides and diamond films epitaxially grown on Si substrates, thereby serving as the foundation for the development and possible commercialization of implantable and stretchable bioelectronic devices that exploit wide bandgap materials.

Tuning the natural frequency of a resonator is an innovative approach for the implementation of mechanical resonators in a broad range of fields such as timing applications, filters or sensors. The conventional electrothermal technique is not favorable towards large tuning range because of its reliance on metallic heating elements. The use of metallic heaters could limit the tuning capability due to the mismatch in thermal expansion coefficients of materials forming the resonator. To solve this drawback, herein, the design, fabrication, and testing of a highly-doped SiC bridge resonator that excludes the use of metallic material as a heating element has been proposed. Instead, free-standing SiC structure functions as the mechanical resonant component as well as the heating element. Through the use of the Joule heating effect, a frequency tuning capability of almost∆f/fo≈80% has been demonstrated. The proposed device also exhibited a wide operating frequency range from 72.3kHz to 14.5kHz. Our SiC device enables the development of highly sensitive resonant-based sensors, especially in harsh environments.

This paper reports on a platform for monolithic integration of piezoelectric and piezoresistive devices on a single chip using the ScAlN/3C-SiC/Si heterostructure. Surface acoustic wave devices with an electromechanical coupling of 3.2% and an out-of-band rejection as high as 18 dB are demonstrated using the excellent piezoelectric properties of ScAlN and low acoustic loss of 3C-SiC. Additionally, a large piezoresistive effect in the low-doped n-type 3C-SiC(100) thin film has been observed, which exceeds the previously reported values in any SiC thin films. The growth of the n-type 3C-SiC thin film was performed using the low pressure chemical vapor deposition technique at 1250 °C and the standard micro-electro-mechanical systems process is used for the fabrication of 3C-SiC piezoresistors. The piezoresistive effect was measured using the bending beam method in different crystallographic orientations. The maximum gauge factor is –47 for the longitudinal [100] orientation. Using the longitudinal and transverse gauge factors for different crystallographic orientations, the fundamental piezoresistive coefficients of the low-doped n-type 3C-SiC thin film are measured to be π 11 = ( − 14.5 ± 1.3 ) × 10 − 11 Pa−1, π 12 = ( 5.5 ± 0.5 ) × 10 − 11 Pa−1, and π 44 = ( − 1.7 ± 0.7 ) × 10 − 11 Pa−1.

This paper presents for the first time the effect of strain on the electrical conductance of p-type nanocrystalline SiC grown on a Si substrate. The gauge factor of the p-type nanocrystalline SiC was found to be 14.5 which is one order of magnitude larger than that in most metals. This result indicates that mechanical strain has a significant influence on the electrical conductance of p-type nanocrystalline SiC, which is promising for mechanical sensing applications in harsh environments.

The piezoresistive effect in silicon nanowires (SiNWs) has attracted a great deal of interest for NEMS devices. Most of the piezoresistive SiNWs reported in the literature were fabricated using the bottom up method or top down processes such as electron beam lithography (EBL). Focused ion beam (FIB), on the other hand, is more compatible with CMOS integration than the bottom up method, and is simpler and more capable of fabricating very narrow Si nanostructures compared to EBL and photolithography. Taking the advantages of FIB, this paper presents for the first time the piezoresistive effect of p-type SiNWs fabricated using focused ion beam implantation and wet etching. The SiNWs were locally amorphized by Ga+ ion implantation, selectively wet-etched, and thermally annealed at 700 °C. A relatively large gauge factor of approximately 47 was found in the annealed SiNWs, indicating the potential of using the piezoresistive effect in top-down fabricated SiNWs for developing NEMS sensors.

This article reports the first results on the strain-induced pseudo-Hall effect in single crystal 3C-SiC(111) four-terminal devices. The impact of crystal orientation and the direction of strain on this effect has been presented. A single crystal p-type 3C-SiC(111) was grown by low pressure chemical vapor deposition and four-terminal devices were fabricated using conventional photolithography and dry etching processes. It has been observed that the pseudo-Hall effect in p-type 3C-SiC(111) is the same in [110] and [11] crystal orientations and is smaller than the pseudo-Hall effect of 3C-SiC(100) four-terminal devices due to the defects associated with the growth of 3C-SiC(111).

This communication reports for the first time, the impact of device geometry on the stress-dependent offset voltage of single crystal p-type 3C–SiC four terminal devices. Single crystal p-type 3C–SiC(100) was grown by low pressure chemical vapor deposition and three different device geometries (cross, rectangle and square) were fabricated using the conventional photolithography and dry etching processes. It was observed that the stress-dependent offset voltage of the devices strongly depends upon the device geometry and it can be increased by almost 100% by just selecting the appropriate device geometry. We also found that as the device is rotated within the (100) crystal plane its stress sensitivity varies from ≈0 to 9 × 10−11 Pa−1.

This paper presents for the first time the orientation dependence of the pseudo-Hall effect in p-type 3C–SiC four-terminal devices under mechanical stress. Experimental results indicate that the offset voltage of p-type 3C–SiC four-terminal devices significantly depends on the directions of the applied current and stress. We also calculated the piezoresistive coefficients π61, π62, and π66, showing that π66 with its maximum value of approximately 16.7 × 10−11 Pa−1 plays a more dominant role than π61 and π62. The magnitude of the offset voltage in arbitrary orientation under stress was estimated based on these coefficients. The finding in this study plays an important role in the optimization of Microelectromechanical Systems (MEMS) mechanical sensors utilizing the pseudo-Hall effect in p-type 3C–SiC.

This paper reports on the thermoresistive properties of graphite on paper (GOP). A negative temperature coefficient of resistance (TCR) from −2900 to −4400 ppm K−1 was observed for the GOP. This negative and large TCR is attributed to an increase in the thermionic emission current over a low potential barrier with increasing temperature. The potential barrier was found to be 33 meV between the graphite grains. The paper also demonstrates the use of the GOP in a highly sensitive (0.83 mV (m s−1)−0.8 mW−1) GOP-based anemometer, indicating strong feasibility of using this material for low-cost and sensitive thermal sensing applications.

This letter reports a giant opto-piezoresistive effect in p-3C-SiC/p-Si heterostructure under visible-light illumination. The p-3C-SiC/p-Si heterostructure has been fabricated by growing a 390 nm p-type 3C-SiC on a p-type Si substrate using the low pressure chemical vapor deposition (LPCVD) technique. The gauge factor of the heterostructure was found to be 28 under a dark condition; however, it significantly increased to about −455 under illumination of 635 nm wavelength at 3.0 mW/cm2. This gauge factor is over 200 times higher than that of commercial metal strain gauge, 16 times higher than that of 3C-SiC thinfilm, and approximately 5 times larger than that of bulk Si. This enhancement of the gauge factor was attributed to the opto-mechanical coupling effect in p-3C-SiC/p-Si heterostructure. The opto-mechanical coupling effect is the amplified effect of the photoconductivity enhancement and strain-induced band structure modification in the p-type Si substrate. These findings enable extremely high sensiti...

This letter reports for the first time the strain dependence of the offset voltage in p-type 3C-SiC van der Pauw square device. The p-type 3C-SiC thin film was epitaxially grown on a p-type Si(100) wafer using low pressure chemical vapor deposition followed by a conventional photolithography and dry etch processes, forming four-terminal van der Pauw device. The influence of applied tensile and compressive strain on the offset voltage of the van der Pauw device was investigated using the bending beam method. Experimental results showed that the offset voltage of the device is significantly changed by applied compressive and tensile strain, indicating the feasibility of using this effect for mechanical sensing applications. The sensitivity of the device to the applied strain has been found to be 70 (mV/A)/ppm.

The current mechanism and effects of external transverse stress in the [110] orientation on the electrical properties of a single crystal (100) p-3C-SiC/p-Si heterojunction diode are reported for the first time. It has been observed that the current flow in the heterojunction is due to tunneling through the triangular potential barrier formed due to valence band offset between Si and SiC. The applied stress produces small changes in tunneling current when stress is increased from 0 to 308 MPa. The observed increase in current at 0.24 V is 10% at maximum stress of 308 MPa. The increase of tunneling current when applying stress is explained in terms of stress, which alters the out-of-plane effective mass, and the effective tunneling barrier height of holes in top subbands of p-type Si.

In this work, we present the design and fabrication of high-frequency SiC nanoresonators for highly sensitive nanoparticle sensing. A 280-nm single crystalline SiC film was grown on a Si wafer, and released from the substrate using an isotropic dry etching process. The SiC nanoresonators were then formed using the Focused Ion Beam technique. The simulation results show that the as-fabricated resonators can be thermally actuated at a very high in-plane resonant frequency of 366.11 MHz, and utilized as sensitive nano-particle sensing elements with a high mass sensitivity of 233 kHz/femtogram. These data indicate the possibility of developing SiC nanoresonators for high-resolution mass sensing and other high-frequency applications.

This paper presents an innovative nano strain-amplifier employed to significantly enhance the sensitivity of piezoresistive strain sensors. Inspired from the dogbone structure, the nano strain-amplifier consists of a nano thin frame released from the substrate, where nanowires were formed at the centre of the frame. Analytical and numerical results indicated that a nano strain-amplifier significantly increases the strain induced into a free standing nanowire, resulting in a large change in their electrical conductance. The proposed structure was demonstrated in p-type cubic silicon carbide nanowires fabricated using a top down process. The experimental data showed that the nano strain-amplifier can enhance the sensitivity of SiC strain sensors at least 5.4 times larger than that of the conventional structures. This result indicates the potential of the proposed strain-amplifier for ultra-sensitive mechanical sensing applications., 4 pages, 5 figures

Cubic silicon carbide is a promising material for Micro Electro Mechanical Systems (MEMS) applications in harsh environ-ments and bioapplications thanks to its large band gap, chemical inertness, excellent corrosion tolerance and capability of growth on a Si substrate. This paper reports the piezoresistive effect of p-type single crystalline 3C-SiC characterized at high temperatures, using an in situ measurement method. The experimental results show that the highly doped p-type 3C-SiC possesses a relatively stable gauge factor of approximately 25 to 28 at temperatures varying from 300 K to 573 K. The in situ method proposed in this study also demonstrated that, the combination of the piezoresistive and thermoresistive effects can increase the gauge factor of p-type 3C-SiC to approximately 20% at 573 K. The increase in gauge factor based on the combination of these phenomena could enhance the sensitivity of SiC based MEMS mechanical sensors.

Hexagonal SiC thin films have been deposited using radio frequency reactive magnetron sputtering technique by varying the substrate temperature and other deposition conditions. Prior to deposition surface modification of the substrate Si(1 0 0) played an important role in deposition of the hexagonal SiC structure. The effect of substrate temperature during deposition on structure, composition and surface morphology of the SiC films has been analyzed using atomic force microscopy, Fourier transform infrared spectroscopy and spectroscopic ellipsometry. X-ray diffraction in conventional θ –2 θ mode and omega scan mode revealed that the deposited films were crystalline having 8H-SiC structure and crystallinity improved with increase of deposition temperature. The bonding order and Si–C composition within the films showed improvement with the increase of deposition temperature. The surface of thin films grew in the shape of globes and columns depending upon deposition temperature. The optical properties also showed improvement with increase of deposition temperature and the results obtained by ellipsometry reinforced the results of other techniques.

We report for the first time a highly sensitive paper-based tactile sensor using laminated graphite drawn on paper. Thanks to the high gauge factor of 26.2, as well as its excellent robustness and humidity-resistance, plastic-laminated graphite-on-paper has a high potential for mechanical sensors. Additionally, the plastic lamination combined with the laser cutting technique proposed in this study would enable the mass production of cleanroom-free fabrication and low-cost MEMS devices.

In this paper, we report on a low-cost, environment-friendly and wearable thermal flow sensor, which can be manufactured in-house using pencil graphite as a sensing hot film and biodegradable printing paper as a substrate, without using any toxic solvents or cleanroom facilities. The hot film flow sensor offers excellent performance such as high signal-to-noise ratio ($\geqslant $ 40 for an air flow velocity of 1 m s−1), high sensitivity to airflow (53.7 mV(m s−1)−0.8) and outstanding long-term stability (almost no drift in 24 h). The sensor can be comfortably affixed to the philtrum of patients and measures human respiration in realtime. The results indicate that the wearable thermal flow sensors fabricated by this solvent-free and user-friendly method could be employed in human respiratory monitoring.

A cost effective and easy to fabricate stress sensor based on pseudo-Hall effect in Graphite on Paper (GOP) has been presented in this article. The four terminal devices were developed by pencil drawing with hand on to the paper substrate. The stress was applied to the paper containing four terminal devices with the input current applied at two terminals and the offset voltage observed at other two terminals called pseudo-Hall effect. The GOP stress sensor showed significant response to the applied stress which was smooth and linear. These results showed that the pseudo-Hall effect in GOP based four terminal devices can be used for cost effective, flexible and easy to make stress, strain or force sensors.

This article reports the results on the piezo-Hall effect in single crystal n-type 3C-SiC(100) having a low carrier concentration. The effect of the crystallographic orientation on the piezo-Hall effect has been investigated by applying stress to the Hall devices fabricated in different crystallographic directions. Single crystal n-type 3C-SiC(100) and 3C-SiC(111) were grown by low pressure chemical vapor deposition at 1250 °C. Fundamental piezo-Hall coefficients were obtained using the piezo-Hall effect measurements as P11 = (–29 ± 1.3) × 10−11 Pa−1, P12 = (11.06 ± 0.5)× 10−11 Pa−1, and P44 = (–3.4 ± 0.7) × 10−11 Pa−1. It has been observed that the piezo-Hall coefficients of n-type 3C-SiC(100) show a completely different behavior as compared to that of p-type 3C-SiC.