Carlos Torres

Naval Information Warfare Center (NIWC) Pacific · Advanced Photonic Technologies Branch (Code 55360)

The vertical transport of non-equilibrium charge carriers through semiconductor heterostructures has led to milestones in electronics with the development of the hot-electron transistor. Recently, significant advances have been made with atomically-sharp heterostructures implementing various two-dimensional materials. Although graphene-base hot-ele...

We demonstrate vertical graphene-base hot-electron transistors (GB-HETs) with a variety of structures and material parameters. Our GB-HETs exhibit a current saturation with a high current on-off ratio (>105), which result from both the vertical transport of hot electrons across the ultra-thin graphene base and the filtering of hot electrons through...

The experimental observation of band-to-band tunneling in novel tunneling field-effect transistors utilizing a monolayer of MoS2 as the conducting channel is demonstrated. Our results indicate that the strong gate-coupling efficiency enabled by two-dimensional materials, such as monolayer MoS2 , results in the direct manifestation of a band-to-band...

Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive coll...

Historically, graphene-based transistor fabrication has been time-consuming due to the high demand for carefully controlled Raman spectroscopy, physical vapor deposition, and lift-off processes. For the first time in a three-terminal graphene field-effect transistor embodiment, we introduce a rapid fabrication technique that implements non-toxic eu...

This technical report summarizes the work executed during FY21-FY23 of the Office of Naval Research (ONR)-funded Electrically-Tunable On-Demand Energy Bandstructures in Pulse Laser Deposited 2D Quantum Material Heterostructure-Based Devices (Qu-PLD) project and during FY21FY22 of the Naval Information Warfare Center (NIWC) Pacific Naval Innovative...

A graphene device for filtering color, involving a graphene structure responsive to continuous in-situ electrical gate-tuning of a Fermi level thereof and a plurality of nanoparticles disposed in relation to the graphene structure, each portion of the plurality of nanoparticles having a distinct energy bandgap in relation to another portion of the...

This Technical Report summarizes the 2D material-based device fabrication procedures executed during the FY17-19 of the Office of Naval Research (ONR) In-House Laboratory Independent Research (ILIR) funded “Voltage-Tunable Wavelength-Agile 2D Material-Based Light-Emitting Transistors (2D-LETs)” project as well as the first year research effort FY20...

This technical document summarizes the recently established and novel capabilities offered by the Quantum-Engineered Nano Devices Laboratory (QENDL) in Code 55360, Advanced Photonic Technologies Branch, Topside Complex, NIWC Pacific, San Diego, CA. Dr. Torres, Jr. served as the principal investigator in the FY18 Naval Innovative Science and Enginee...

This paper discusses the production and investigation of novel graphene switches by gating through an electrical double layer (EDL). Controlled voltage biases across a liquid dielectric and graphene induce electrochemical reactions within the dielectric and produce high electric fields in an EDL at the surface of graphene. As the electrochemical re...

A novel integration technique is demonstrated that combines 2-D graphene with galinstan (eutectic gallium-based alloy) into flexible, compact, and durable devices. This unique combination enables the next-generation electronic devices with miniaturized microfluidic capabilities. Robust performance is exhibited across a wide range of flexure with le...

Quantum increment gate [1] is a kind of the basic quantum operator, which is the generalized CNOT gate. Be different with quantum adder operator, it can be operated on n qubits producing cyclic permutation in the 2n bit-string states [17]. The so-called increment gate means that the value of the input register could be incremented by 1 according to...

The quantum incrementer is one of the simplest quantum operators, which exhibits basic arithmetic operations such as addition, the propagation of carry qubits and the resetting of carry qubits. In this paper, three quantum incrementer gate circuit topologies are derived and compared based upon their total number of gates, the complexity of the circ...

We present the analysis of linewidth roughness (LWR) in nanowire-mask-based graphene nanoribbons (GNRs) and evaluate its impact on the device performance. The data show that the LWR amplitude decreases with the GNR width, possibly due to the etching undercut near the edge of a nanowire-mask. We further discuss the large variation in GNR devices in...

We report an experimental investigation of the edge effect on the room-temperature transport in graphene nanoribbon and graphene sheet (both single-layer and bilayer). By measuring the resistance scaling behaviors at both low- and high-carrier densities, we show that the transport of single-layer nanoribbons lies in a strong localization regime, wh...

Conductance fluctuation is usually unavoidable in graphene nanoribbons (GNR) due to the presence of disorder along its edges. By measuring the low-frequency noise in GNR devices, we find that the conductance fluctuation is strongly correlated with the density-of-states of GNR. In single-layer GNR, the gate-dependence of noise shows peaks whose posi...

Scattering mechanisms in graphene are critical to understanding the limits of signal-to-noise ratios of unsuspended graphene devices. Here we present the four-probe low-frequency noise (1/f) characteristics in back-gated single layer graphene (SLG) and bilayer graphene (BLG) samples. Contrary to the expected noise increase with the resistance, the...

We present a graphene nanoribbon fabrication method based on a nanowire mask. Using a four-probe setup, single-layer nanoribbon (SLR) and bilayer nanoribbon (BLR) show low-frequency noise levels lower than (comparable to) the SLRs (BLRs) achieved by hydrogen-silsesquioxane based methods. Submicron channel SLR and BLR both show conductance quantizat...

In this work, we present a GNR fabrication method based on a 9 nanowire-mask, where the edge roughness is determined by the surface roughness of the nanowire (<;1nm)² . With four-terminal measurement setup, single layer nanoribbon (SLR) devices show μ_hole~1180cm²/(Vs), I_on/I_οff >7 and low frequ...

The unique density of states of graphene at the device level is probed via tunneling spectroscopy of macroscopic metal-oxide-graphene structures. Local conductance minima from electrons tunneling into the graphene Dirac point are observed in the dI/dV spectra of both the single-junction and dual-junction configurations. Nonequally-spaced Landau lev...

We report the observation of electron-hole puddle induced scattering in both monolayer and bilayer bulk graphene at the low carrier density regime (near the Dirac point) using four-probe low frequency noise measurements. For monolayer graphene, the non-uniformity of the localized density of states in the presence of puddles results in an abnormal n...