In this work, the operation of n- and p-type field-effect transistors (FETs) on the same WSe2 flake is realized,and a complementary logic inverter is demonstrated. The p-FET is fabricated by contacting WSe2 with a high work function metal, Pt, which facilities hole injection at the source contact. The n-FET is realized by utilizing selective surface charge transfer doping with potassium to form degenerately doped n+ contacts for electron injection. An ON/OFF current ratio of >10(4) is achieved for both n- and p-FETs with similar ON current densities. A dc voltage gain of >12 is measured for the complementary WSe2 inverter. This work presents an important advance toward realization of complementary logic devices based on layered chalcogenide semiconductors for electronic applications.
A flexible
and wearable microsensor array is described for simultaneous
multiplexed monitoring of heavy metals in human body fluids. Zn, Cd,
Pb, Cu, and Hg ions are chosen as target analytes for detection via
electrochemical square wave anodic stripping voltammetry (SWASV) on
Au and Bi microelectrodes. The oxidation peaks of these metals are
calibrated and compensated by incorporating a skin temperature sensor.
High selectivity, repeatability, and flexibility of the sensor arrays
are presented. Human sweat and urine samples are collected for heavy
metal analysis, and measured results from the microsensors are validated
through inductively coupled plasma mass spectrometry (ICP-MS). Real-time
on-body evaluation of heavy metal (e.g., zinc and copper) levels in
sweat of human subjects by cycling is performed to examine the change
in concentrations with time. This platform is anticipated to provide
insightful information about an individual’s health state such
as heavy metal exposure and aid the related clinical investigations.
Monolithic 3D integrated circuits using transition metal dichalcogenide materials and low-temperature processing are reported. A variety of digital and analog circuits are implemented on two sequentially integrated layers of devices. Inverter circuit operation at an ultralow supply voltage of 150 mV is achieved, paving the way to high-density, ultralow-voltage, and ultralow-power applications.
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