Atomistic Compositional Details and Their Importance for Spin Qubits in Isotope-Purified Silicon Quantum Wells.

Understanding crystal characteristics down to the atomistic level increasingly emerges as a crucial insight for creating solid state platforms for qubits with reproducible and homogeneous properties. Here, isotope concentration depth profiles in a SiGe/Si/SiGe heterostructure are analyzed with atom probe tomography (APT) and time-of-flight secondary-ion mass spectrometry down to their respective limits of isotope concentrations and depth resolution. Spin-echo dephasing times and valley energy splittings E around have been observed for single spin qubits in this quantum well (QW) heterostructure, pointing toward the suppression of qubit decoherence through hyperfine interaction with crystal host nuclear spins or via scattering between valley states.

Ultrasteep Slope Cryogenic FETs Based on Bilayer Graphene.

Cryogenic field-effect transistors (FETs) offer great potential for applications, the most notable example being classical control electronics for quantum information processors. For the latter, on-chip FETs with low power consumption are crucial. This requires operating voltages in the millivolt range, which are only achievable in devices with ultrasteep subthreshold slopes.

Delineating charge and capacitance transduction in system-integrated graphene-based BioFETs used as aptasensors for malaria detection.

Despite significant eradication efforts, malaria remains a persistent infectious disease with high mortality due to the lack of efficient point-of-care (PoC) screening solutions required to manage low-density asymptomatic parasitemia. In response, we demonstrate a quantitative electrical biosensor based on system-integrated two-dimensional field-effect transistors (2DBioFETs) of reduced graphene oxide (rGO) as transducer for high sensitivity screening of the main malaria biomarker, Plasmodium falciparum lactate dehydrogenase (PfLDH). The 2DBioFETs were biofunctionalized with pyrene-modified 2008s aptamers as specific PfLDH receptors.

Turning Low-Nanoscale Intrinsic Silicon Highly Electron-Conductive by SiO Coating.

Impurity doping in silicon (Si) ultra-large-scale integration is one of the key challenges which prevent further device miniaturization. Using ultraviolet photoelectron spectroscopy and X-ray absorption spectroscopy in the total fluorescence yield mode, we show that the lowest unoccupied and highest occupied electronic states of ≤3 nm thick SiO-coated Si nanowells shift by up to 0.2 eV below the conduction band and ca.

High-Q inverted silica microtoroid resonators monolithically integrated into a silicon photonics platform.

We report on the monolithic integration of a new class of reflown silica microtoroid resonators with silicon nanowaveguides fabricated on top of the silica film. Connectivity with other silicon photonics devices is enabled by inversion of the toroid geometry, defined by etching a circular opening rather than a disk in an undercut silica membrane. Intrinsic quality factors of up to 2 million are achieved and several avenues of process improvement are identified that can help attain the higher quality factors (> 10) that are possible in reflown microtoroids.

Intrinsic ultrasmall nanoscale silicon turns n-/p-type with SiO/SiN-coating.

Impurity doping of ultrasmall nanoscale (usn) silicon (Si) currently used in ultralarge scale integration (ULSI) faces serious miniaturization challenges below the 14 nm technology node such as dopant out-diffusion and inactivation by clustering in Si-based field-effect transistors (FETs). Moreover, self-purification and massively increased ionization energy cause doping to fail for Si nano-crystals (NCs) showing quantum confinement. To introduce electron- (n-) or hole- (p-) type conductivity, usn-Si may not require doping, but an energy shift of electronic states with respect to the vacuum energy between different regions of usn-Si.

Optimizing the identification of mono- and bilayer graphene on multilayer substrates.

This work presents an investigation and optimization of the identification of graphene mono- and bilayers on various multilayer substrates. Instead of the mere contrast between substrate and substrate/mono/bilayer systems, weighted color differences are used to obtain optimum visibility. Our approach employs a genetic algorithm that allows finding the most appropriate composition of multilayer systems in terms of materials in use and their respective thicknesses.

Donor deactivation in silicon nanostructures.

The operation of electronic devices relies on the density of free charge carriers available in the semiconductor; in most semiconductor devices this density is controlled by the addition of doping atoms. As dimensions are scaled down to achieve economic and performance benefits, the presence of interfaces and materials adjacent to the semiconductor will become more important and will eventually completely determine the electronic properties of the device. To sustain further improvements in performance, novel field-effect transistor architectures, such as FinFETs and nanowire field-effect transistors, have been proposed as replacements for the planar devices used today, and also for applications in biosensing and power generation.

Doping limits of grown in situ doped silicon nanowires using phosphine.

Structural characterization and electrical measurements of silicon nanowires (SiNWs) synthesized by Au catalyzed vapor-liquid-solid growth using silane and axially doped in situ with phosphine are reported. We demonstrate that highly n-doped SiNWs can be grown without structural defects and high selectivity and find that addition of the dopant reduces the growth rate by less than 8% irrespective of the radius. This indicates that also the dopant incorporation is radius-independent.

Low-frequency current fluctuations in individual semiconducting single-wall carbon nanotubes.

We present a systematic study on low-frequency current fluctuations of nanodevices consisting of one single semiconducting nanotube, which exhibit significant 1/f-type noise. By examining devices with different switching mechanisms, carrier types (electrons vs holes), and channel lengths, we show that the 1/f fluctuation level in semiconducting nanotubes is correlated to the total number of transport carriers present in the system. However, the 1/f noise level per carrier is not larger than that of most bulk conventional semiconductors, e.

The role of metal-nanotube contact in the performance of carbon nanotube field-effect transistors.

Single-wall carbon nanotube field-effect transistors (CNFETs) have been shown to behave as Schottky barrier (SB) devices. It is not clear, however, what factors control the SB size. Here we present the first statistical analysis of this issue.