The optical response of semiconducting monolayer transition-metal dichalcogenides (TMDCs) is dominated by strongly bound excitons that are stable even at room temperature. However, substrate-related effects such as screening and disorder in currently available specimens mask many anticipated physical phenomena limit device applications TMDCs. Here, we demonstrate these undesirable suppressed suspended devices. Extremely robust (photogain > 1,000) fast (response time < 1 ms) photoresponse...

We investigate near-field energy transfer between chemically synthesized quantum dots (QDs) and two-dimensional semiconductors. fabricate devices in which electrostatically gated semiconducting monolayer molybdenum disulfide (MoS2) is placed atop a homogenous self-assembled layer of core-shell CdSSe QDs. demonstrate efficient non-radiative F\"orster resonant (FRET) from QDs into MoS2 prove that modest gate-induced variation the excitonic absorption lead to large (~500%) changes FRET rate....

An ultraviolet (UV) photodetector employing the two-dimensional electron gas (2DEG) formed at AlGaN/GaN interface as an interdigitated transducer (IDT) is characterized under optical stimulus. The 2DEG-IDT exhibits a record high normalized photocurrent-to-dark current ratio of 6 × 1014. We also observe responsivity (7800 A/W) and ultraviolet–visible rejection (106), among highest reported values for any GaN architecture. argue that valence band offset in heterostructure essential achieving...

We explore the dependence of electrical transport in a graphene field effect transistor (GraFET) on flow water/sodium chloride electrolyte within immediate vicinity that transistor. find large and reproducible shifts charge neutrality point GraFETs are dependent liquid velocity ion concentration. show these consistent with variation local electrochemical potential next to caused by fluid (streaming potential). Furthermore, we utilize sensitivity parameters demonstrate graphene-based mass...

We have evaluated the responses of graphene materials and devices to 10-keV X-ray irradiation ozone exposure. Large positive shifts are observed in current-voltage characteristics graphene-on- SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> transistors irradiated under negative gate bias. Moreover, significant radiation-induced increases found resistance suspended layers; charge neutral point (CNP) layer also positively with...

Van der Waals (vdW) heterostructures consisting of two dimensional materials offer a platform to obtain material by design and are very attractive owing novel electronic states. Research on 2D van (vdWH) has so far been focused fabricating individually stacked atomically thin unary or binary crystals. Such systems include graphene (Gr), hexagonal boron nitride (h-BN) member the transition metal dichalcogenides family. Here we present our experimental study opto-electronic properties...

Scalable fabrication of high quality photodetectors derived from synthetically grown monolayer transition metal dichalcogenides is highly desired and important for wide range nanophotonics applications. We present here scalable MoS2 on sapphire substrates through an efficient process, which includes growing large scale via chemical vapor deposition (CVD), multi-step optical lithography device patterning electrodes fabrication. In every measured device, we observed the following universal...

Layered materials based on transition-metal dichalcogenides (TMDs) are promising for a wide range of electronic and optoelectronic devices. Realizing such practical applications often requires metal–TMD connections or contacts. Hence, complete understanding band alignments potential barrier heights governing the transport through junctions is critical. However, it presently unclear how energy bands TMD align while in contact with metal as function number layers. In pursuit removing this...

This paper presents a demonstration of 278 V GaN avalanche photodiode offering photoresponsivity 60 A/W and capable operating at high temperature with gain 105. The n–i–p diode fabricated on free-standing substrate showed robust avalanche, which has not been observed any photodiodes (APDs) grown foreign substrates. Both electrical optical characterization studies were conducted to validate the occurrence in these devices. device positive coefficient breakdown voltage, follows nature...

We employ resistance measurements and Raman spectroscopy to investigate the effects of UV ozone (UVO) exposure Ar annealing on graphene-on-SiO2 transistors. Shorter UVO exposures lead oxygen adsorption doping; longer significant defect generation then etching. Elevated-temperature following leads local healing, as shown by evolution characteristic D- G-peaks. In striking contrast, overall graphene transistor increases significantly due void formation. Density functional calculations show...

Electrical stress and 10-keV x-ray irradiation annealing responses are evaluated for back-gate MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> transistors. Relative stability of device characteristics is observed constant-voltage stress. The drain current decreases significantly after both positive negative bias irradiation. Density functional theory calculations ozone exposure experiments suggest that O atoms adsorbed on the surface...

Atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDCs) are attractive materials for next generation nanoscale optoelectronic applications. Understanding optical behavior of the edges and grain boundaries synthetically grown TMDCs is vital optimizing their properties. Elucidating properties 2D through far-field microscopy requires a diffraction-limited beam diameter sub-micron in size. Here we present our experimental work on spatial photoluminescence (PL) scanning...

We have found experimentally that the shot noise of tunneling current I through an undoped semiconductor superlattice is reduced with respect to Poissonian value 2eI, and approaches 1/3 in superlattices whose quantum wells are strongly coupled. On other hand, when coupling weak or a strong electric field applied superlattice, becomes Poissonian. Although our results qualitatively consistent existing theories for one-dimensional multibarrier structures, cannot account dependence on parameters...

Quantum mechanical-based kinetic Monte-Carlo calculations (KMC) are used to investigate mechanisms of degradation graphene devices subjected 10-keV x-ray irradiation, ozone exposure, and subsequent high-temperature annealing. Using KMC, we monitor the time evolution defect concentrations on a surface. The mechanism for oxygen exposure anneal surface greatly depends temperature initial H O atoms At coverage ~0.05 higher, damage is caused by formation vacancies due desorption CO <sub...

We report the phenomenon of extraordinary electroconductance in microscopic metal-semiconductor hybrid structures fabricated from GaAs epitaxial layer and a Ti thin film shunt. Four-lead Van der Pauw show gain 5.2% under +2.5kV∕cm with zero shunt bias. The increase sample conductance results thermionic field emission electrons geometrical amplification. A model provides good agreement experimental data clearly demonstrates geometry dependence effect (EEC). differences between EEC devices...

We report on the magnetotransport in a 90 nm thick n-type GaAs epitaxial thin film weak localization (WL) regime. Low temperature (T</=50 K) data are fit with WL theory, from which phase coherence time, tau(varphi) proportional, variantT(-p) (p=1.22+/-0.01), extracted. conclude that dominant dephasing mechanism at these temperatures is electron-electron (e-e) scattering Nyquist limit. Evidence of crossover two-dimensional to three-dimensional behavior respect both coherent transport and e-e...

We report an individually addressable Ti∕GaAs metal-semiconductor hybrid optical nanosensor with positive photoresistance and a sensitivity that increases as the device dimensions shrink. The underlying physics relates to crossover from ballistic diffusive transport of photoinduced carriers geometric enhancement effect associated Schottky-barrier-coupled parallel metal shunt layer. For 250 nm under 633 illumination we observe specific detectivity D(*)=5.06×10(11) cm √Hz∕W dynamic response 40 dB.

We have found experimentally that the shot noise in InAlAs-InGaAs-InAlAs Triple-Barrier Resonant-Tunneling Diodes (TBRTD) is reduced over 2eI Poissonian value whenever their differential conductance positive, and enhanced when negative. This behavior, although qualitatively similar to double-barrier diodes, differs from it important details. In TBRTDs reduction considerably larger than predicted by a semi-classical model, enhancement does not correlate with strength of negative conductance....

We present a comprehensive study of phenomenon, extraordinary electroconductance (EEC), in microscopic metal-semiconductor hybrid (MSH) structures at room temperature. Our artificially designed MSH structure shows highly efficient external electric field sensing properties not exhibited by bare semiconductor structures. The device is fabricated from GaAs epitaxial layer with Ti/Au shunt subject to an and gives maximum 5.2% EEC effect corresponding resolution 3.05 V/cm bias 2.5 kV/cm....

Atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDs), such as MoS$_2$, are promising candidates for nanoscale photonics because of strong-light matter interactions. However, Fermi level pinning due to metal-induced gap (MIGS) states at the metals-monolayer MoS$_2$ interface limits application optoelectronic devices based on conventional metals high contact resistance Schottky contacts. On other hand, a semimetal-TMD-semimetal device can overcome this limitation, where...

Owing to its wide (3.4 eV) and direct-tunable band gap, gallium nitride (GaN) is an excellent material platform make UV photo detectors. GaN also stable in radiation-rich high-temperature environments, which makes detectors fabricated using this useful for in-situ flame detection combustion monitoring. In paper, we use a detector measure ultraviolet (UV) emissions from hybrid rocket motor igniter plume. The detector, built at the Stanford Nanofabrication Facility, has 5 μm regions of...

We present vibrational properties of Franckeite, which is a naturally occurring van der Waals heterostructure consisting two different semiconducting layers. Franckeite complex layered crystal composed alternating SnS2-like pseudohexagonal and PbS-like pseudotetragonal layers stacked on top each other, providing unique platform to study thermal transport across with mass density phonon mismatches. Using micro-Raman spectroscopy first-principles Raman simulations, we found that the structure...

This abstract presents a study on the avalanche capability of GaN p-i-n diode leading to achievement 60A/W, 278V photodiode. The fabricated free-standing substrate was capable due optimal edge termination. Both electrical and optical characterizations were conducted validate occurrence in these devices. device showed positive temperature coefficient breakdown voltage, which follows nature breakdown. measured be 3.85 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML"...