Mobility Extraction in 2D Transition Metal Dichalcogenide Devices-Avoiding Contact Resistance Implicated Overestimation.

Schottky barrier (SB) transistors operate distinctly different from conventional metal-oxide semiconductor field-effect transistors, in a unique way that the gate impacts the carrier injection from the metal source/drain contacts into the channel region. While it has been long recognized that this can have severe implications for device characteristics in the subthreshold region, impacts of contact gating of SB in the on-state of the devices, which affects evaluation of intrinsic channel properties, have been yet comprehensively studied. Due to the fact that contact resistance (R ) is always gate-dependent in a typical back-gated device structure, the traditional approach of deriving field-effect mobility from the maximum transconductance (g ) is in principle not correct and can even overestimate the mobility.

Plasmonic Sensing Studies of a Gas-Phase Cystic Fibrosis Marker in Moisture Laden Air.

A plasmonic sensing platform was developed as a noninvasive method to monitor gas-phase biomarkers related to cystic fibrosis (CF). The nanohole array (NHA) sensing platform is based on localized surface plasmon resonance (LSPR) and offers a rapid data acquisition capability. Among the numerous gas-phase biomarkers that can be used to assess the lung health of CF patients, acetaldehyde was selected for this investigation.

A Cloud-connected NO and Ozone Sensor System for Personalized Pediatric Asthma Research and Management.

This paper presents a cloud-connected indoor air quality sensor system that can be deployed to patients' homes to study personal microenvironmental exposure for asthma research and management. The system consists of multiple compact sensor units that can measure residential NO, ozone, humidity, and temperature at one-minute resolution and a cloud-based informatic system that acquires, stores, and visualizes the microenvironmental data in real-time. The sensor hardware can measure NO as low as 10 ppb and ozone at 15 ppb.

Integrated contact lens sensor system based on multifunctional ultrathin MoS transistors.

Smart contact lenses attract extensive interests due to their capability of directly monitoring physiological and ambient information. However, previous demonstrations usually lacked efficient sensor modalities, facile fabrication process, mechanical stability, or biocompatibility. Here, we demonstrate a flexible approach for fabrication of multifunctional smart contact lenses with an ultrathin MoS transistors-based serpentine mesh sensor system.

Discrimination of 1- and 2-Propanol by Using the Transient Current Change of a Semiconducting ZnFe O Chemiresistor.

A semiconducting metal oxide (SMO) chemiresistor (ZnFe O ) is used for discriminating two isomeric volatile organic compounds (VOCs), namely 1- and 2-propanol. The transient current of the SMO chemiresistor is correlated with the aerobic oxidation of organic vapors on its surface. The changes in transient current of the ZnFe O chemiresistor are measured at different temperatures (260-320 °C) for detecting equal concentrations (200 ppm) of the two structural isomers of propanol.

Generation and enhancement of surface acoustic waves on a highly doped p-type GaAs substrate.

Surface acoustic waves (SAWs) have been widely studied due to their unique advantage to couple the mechanical, electrical, and optical characteristics of semiconductor materials and have successfully been used in many industrial applications. In this work, we report a design that uses piezoelectric material Zinc Oxide (ZnO) to enhance the generation and propagation of SAWs on the surface of a highly doped p-type Gallium Arsenide (GaAs) substrate, which is more extensively used in optoelectronic devices than intrinsic GaAs structures. To maximize the piezoelectricity and successfully generate SAWs, high quality -axis orientation of the ZnO film is needed; thus we experiment and develop optimized recipes of a radio frequency (RF) magnetron sputtering system to deposit ZnO on the GaAs substrate.

Miniaturized nanohole array based plasmonic sensor for the detection of acetone and ethanol with insights into the kinetics of adsorptive plasmonic sensing.

The present work demonstrates development of a miniaturized plasmonic platform comprised of a Au nanohole array (NHA) on a Si/Si3N4 substrate. Plasmonic responses of the NHA platform, which is coated with Cu-benzenetricarboxylate metal organic framework (MOF), are found to be promising even towards 500 nmol mol-1 (ppb) of acetone or ethanol vapors at room temperature. The sensing characteristics are further investigated by varying the operating temperature (296 K to 318 K) of the sensor and the concentrations of vapors (500 nmol mol-1 to 320 μmol mol-1).

Tuning the Polarity of MoTe FETs by Varying the Channel Thickness for Gas-Sensing Applications.

In this study, electrical characteristics of MoTe field-effect transistors (FETs) are investigated as a function of channel thickness. The conductivity type in FETs, fabricated from exfoliated MoTe crystals, switched from p-type to ambipolar to n-type conduction with increasing MoTe channel thickness from 10.6 nm to 56.

Control of polarity in multilayer MoTe field-effect transistors by channel thickness.

In this study, electronic properties of field-effect transistors (FETs) fabricated from exfoliated MoTe single crystals are investigated as a function of channel thickness. The conductivity type in FETs gradually changes from n-type for thick MoTe layers (above ≈ 65 nm) to ambipolar behavior for intermediate MoTe thickness (between ≈ 60 and 15 nm) to p- type for thin layers (below ≈ 10 nm). The n-type behavior in quasi-bulk MoTe is attributed to doping with chlorine atoms from the TeCl transport agent used for the chemical vapor transport (CVT) growth of MoTe.

Electronic Characteristics of MoSe and MoTe for Nanoelectronic Applications.

Single-crystalline MoSe and MoTe platelets were grown by Chemical Vapor Transport (CVT), followed by exfoliation, device fabrication, optical and electrical characterization. We observed that for the field-effect-transistor (FET) channel thickness in range of 5.5 nm to 8.

An Antimony Selenide Molecular Ink for Flexible Broadband Photodetectors.

The need for low-cost high-performance broadband photon detection with sensitivity in the near infrared (NIR) has driven interest in new materials that combine high absorption with traditional electronic infrastructure (CMOS) compatibility. Here, we demonstrate a facile, low-cost and scalable, catalyst-free one-step solution-processed approach to grow one-dimensional SbSe nanostructures directly on flexible substrates for high-performance NIR photodetectors. Structural characterization and compositional analyses reveal high-quality single-crystalline material with orthorhombic crystal structure and a near-stoichiometric Sb/Se atomic ratio.

Gas Sensing with Bare and Graphene-covered Optical Nano-Antenna Structures.

The motivation behind this work is to study the gas phase chemical sensing characteristics of optical (plasmonic) nano-antennas (ONA) and graphene/graphene oxide-covered versions of these structures. ONA are devices that have their resonating frequency in the visible range. The basic principle governing the detection mechanism for ONA is refractive index sensing.

Compact optical microfluidic uric acid analysis system.

We designed, fabricated and tested a novel compact fluorescence analysis system for quantification of uric acid (UA) in clinical samples at the point-of-care. To perform an analysis, diluted saliva, urine or blood samples are simply placed in a disposable thin-film sample holder using a dropper. A new enzyme immobilization technique was developed to retain within the sample holder two enzymes and a molecule, which transforms into a fluorescer in amounts depending on the UA concentration.

Computational methodology for absolute calibration curves for microfluidic optical analyses.

Optical fluorescence and absorption are two of the primary techniques used for analytical microfluidics. We provide a thorough yet tractable method for computing the performance of diverse optical micro-analytical systems. Sample sizes range from nano- to many micro-liters and concentrations from nano- to milli-molar.