Wafer-scale nanofabrication of telecom single-photon emitters in silicon

A highly promising route to scale millions of qubits is to use quantum photonic integrated circuits (PICs), where deterministic photon sources, reconfigurable optical elements, and single-photon detectors are monolithically integrated on the same silicon chip. The isolation of single-photon emitters, such as the G centers and W centers, in the optical telecommunication O-band, has recently been realized in silicon. In all previous cases, however, single-photon emitters were created uncontrollably in random locations, preventing their scalability. Here, we report the controllable fabrication of single G and W centers in silicon wafers using focused ion beams (FIB) with high probability. We also implement a scalable, broad-beam implantation protocol compatible with the complementary-metal-oxide-semiconductor (CMOS) technology to fabricate single telecom emitters at desired positions on the nanoscale. Our findings unlock a clear and easily exploitable pathway for industrial-scale photonic quantum processors with technology nodes below 100 nm

Extending the coherence time of spin defects in hBN enables advanced qubit control and quantum sensing

Spin defects in hexagonal Boron Nitride (hBN) attract increasing interest for quantum technology since they represent optically-addressable qubits in a van der Waals material. In particular, negatively-charged boron vacancy centers (${V_B}^-$) in hBN have shown promise as sensors of temperature, pressure, and static magnetic fields. However, the short spin coherence time of this defect currently limits its scope for quantum technology. Here, we apply dynamical decoupling techniques to suppress magnetic noise and extend the spin coherence time by nearly two orders of magnitude, approaching the fundamental $T_1$ relaxation limit. Based on this improvement, we demonstrate advanced spin control and a set of quantum sensing protocols to detect electromagnetic signals in the MHz range with sub-Hz resolution. This work lays the foundation for nanoscale sensing using spin defects in an exfoliable material and opens a promising path to quantum sensors and quantum networks integrated into ultra-thin structures

Metal–Insulator Transition via Ion Irradiation in Epitaxial La 0.7 Sr 0.3 MnO 3− δ Thin Films

Complex oxides provide rich physics related to ionic defects. For the proper tuning of functionalities in oxide heterostructures, it is highly desired to develop fast, effective, and low-temperature routes for the dynamic modification of defect concentration and distribution. Herein, the use of helium implantation to efficiently control the vacancy profiles in epitaxial La0.7Sr0.3MnO3−δ thin films is reported. The viability of this approach is supported by lattice expansion in the out-of-plane lattice direction and dramatic change in physical properties, i.e., a transition from ferromagnetic metallic to antiferromagnetic insulating. In particular, a significant increase of resistivity up to four orders of magnitude is evidenced at room temperature, upon implantation of highly energetic He ions. The result offers an attractive means for tuning the emergent physical properties of oxide thin films via strong coupling between strain, defects, and valence

Vegetation response to exceptional global warmth during Oceanic Anoxic Event 2

The Cenomanian–Turonian Oceanic Anoxic Event (OAE2; ~94.5 million years ago) represents an episode of global-scale marine anoxia and biotic turnover, which corresponds to one of the warmest time intervals in the Phanerozoic. Despite its global significance, information on continental ecosystem response to this greenhouse episode is lacking. Here we present a terrestrial palynological record combined with marine-derived temperature data (TEX86) across an expanded OAE2 section from the Southern Provençal Basin, France. Despite high TEX86-derived temperature estimates reaching up to 38 °C, the continental hinterland did support a diverse vegetation, adapted to persist under elevated temperatures. A transient phase of climatic instability and cooling during OAE2 known as Plenus Cold Event (PCE) is marked by the proliferation of open, savanna-type vegetation rich in angiosperms at the expanse of conifer-dominated forest ecosystems. A rise in early representatives of Normapolles-type pollen during the PCE marks the initial radiation of this important angiosperm group

Presentation on 'Junctionless Nanowire Transistors: From Devices to Sensing Applications' for NanoNet+ Annual Workshop 2023

Downscaling of complementary metal-oxide-semiconductor (CMOS) technology is fraught with difficulties. As a result, novel devices and circuits, sophisticated nanomaterials, and enhanced fabrication processes have become increasingly important in recent decades. Particularly, silicon nanowires have been employed effectively in innovative electronic devices, including sensors, solar cells and in logic circuitry. Due to their high surface to volume ratio, silicon nanowires have been demonstrated as energy efficient devices, which is the key for the next generation of information processing . Field-effect-transistors based on silicon nanowires have been extensively used for sensing applications since the compact nanoscale structures allow excellent regulation of electrostatic potential across the nanowire channel. One such nanowire concept is junctionless nanowire transistor (JNT). A JNT is a highly doped nanowire channel without p-n junctions, where the gate electrode regulates the flow of charge carriers. Silicon JNTs have shown excellent sensitivity to record-low concentrations of the protein streptavidin in liquid phase. However, they have not yet been operated as gas sensors. In this work, we report the fabrication and characterization of silicon-based JNT devices and their initial tests as gas sensors. Intrinsic silicon-on-insulator (SOI) substrates are ion-implanted with phosphorus (n-type) dopant. Millisecond range flash lamp annealing (FLA) is used for dopant activation and implantation defect healing. Top-down approach is carried out for nanowire fabrication using electron beam lithography patterning of the negative resist HSQ followed by reactive ion etching. Successive processes of rapid thermal oxidation and atomic layer deposition are performed to create SiO2 and Al2O3 shell around the silicon nanowires, respectively. UV lithography and metal evaporation are employed to create 50 nm thick Nickel contacts to the nanowires. Electrical characterization of these JNTs is performed by back and top gating the nanowires. Unipolar device behavior is observed . However, these characteristics are changed after contact annealing leading to the ambipolarity in the devices. These devices exhibit an on/off ratio of ~106. To further investigate the ambipolar nature of the silicon JNTs, output characteristics are measured, which shows Schottky barrier-based behavior of the devices. Furthermore, van der Pauw and Hall Effect measurements are performed to determine their carrier concentration and hall mobility. Successive measurements of electrical characteristics of these devices are also performed in vacuum to compare them with the usual ambient measurements. Unfunctionalized JNTs are tested as sensors in purified air and NO2 atmosphere. These sensor tests exhibited characteristic shifts in the transfer curve and a systematic increase and decrease of p- and n-type current, respectively, under the influence of NO2. These tests confirmed the potential suitability of the ambipolar JNT as sensors in gaseous environment. Additionally, these devices will be functionalized and tested for electrical detection of atmospheric free radicals

Data publication: Coherent coupling of metamaterial resonators with dipole transitions of boron acceptors in Si

FTIR transmission spectra of the samples at various temperature

Depth selective magnetic phase coexistence in FeRh thin films

We demonstrate the manipulation of magnetic phases in FeRh thin films through atomic displacements and the distribution of structural defects. Atomic scale disorder can be controlled via irradiation with light noble gas ions, producing depth-varying nanoscale phase configurations of distinct antiferromagnetic, ferromagnetic, and paramagnetic regions. Here, we perform a spatial characterization of the magnetic phases and the local magnetic environment around the Fe atoms, as well as the variation of the open-volumes around atomic sites. Thus, a direct correspondence between the existence of the three magnetic phases and lattice defects is revealed. By careful selection of the irradiating fluence, we show that it is possible to produce simple and thermally stable magnetic configurations, such as uniform magnetization or a bilayer phase structure. Furthermore, the thin film surface and interfaces are observed as the nucleation sites for the transitions between the phases. These results demonstrate a sensitive nanoscale manipulation of magnetic properties, shedding light on magnetic ordering in alloy lattices and broadening the scope for applications.ISSN:2166-532

Implantace energetických Au iontů do ZnO nanopilířů pro modulaci optické odezvy

Nanopillars of ZnO were implanted with Au-400 keV ions at various ion fluences from 1 x 10(15) cm(-2) to 1 x 10(16) cm(-2) and subsequently annealed at 750 degrees C for 15 min in order to reduce the implantation damage and to support Au nanoparticle (NP) aggregation. It was found that implantation-induced effects and thermal effects influence the Au NP coalescence as well as the quality of the ZnO nanopillars. Rutherford Back-Scattering spectrometry (RBS) showed the broader Au-depth profiles than it was theoretically predicted, but the Au-concentration maximum agrees well with prediction taking into account the effective ZnO layer density. The implantation at the higher fluences induced the morphology modification of the nanopillar layer evidenced by RBS and scanning electron microscopy (SEM). An indirect evidence of this effect was given by optical ellipsometry due to gradual refractive index changes in the ZnO nanopillars with the increased Au-ion fluence. Optical characterization of the Au-implanted and annealed nanopillars performed by means of photoluminescence (PL) and diffuse-reflectance spectroscopy (DRS) evidenced the surface plasmon resonance (SPR) activity of the embedded Au NPs. The SPR-enhanced scattering and PL emission observed in the spectral range 500-650 nm are ascribed to Au NPs or more complex Au-clusters. In addition, the ellipsometry measurements of extinction coefficient are found to corroborate well results from DRS, both indicating increase of SPR effect with the increase of Au-ion fluence and after the post-annealing.Do nanopilířů ZnO byly implantovány ionty Au-400 keV při různých fluktuacích iontů od 1 x 10(15) cm(-2) do 1 x 10(16) cm(-2) a následně žíhány při 750 stupních C po dobu 15 min, aby se snížilo poškození implantace a podpořila se agregace nanočástic Au (NP). Bylo zjištěno, že efekty vyvolané implantací a tepelné efekty ovlivňují koalescenci Au NP a také kvalitu nanopilířů ZnO. Rutherfordova zpětná rozptylová spektrometrie (RBS) ukázala širší profily hloubky Au, než bylo teoreticky předpovězeno, ale maximum koncentrace Au dobře souhlasí s predikcí, která bere v úvahu efektivní hustotu vrstvy ZnO. Implantace při vyšších fluencesách vyvolala morfologickou modifikaci nanopilární vrstvy doloženou RBS a rastrovací elektronovou mikroskopií (SEM). Nepřímý důkaz tohoto efektu poskytla optická elipsometrie v důsledku postupných změn indexu lomu v nanopilárech ZnO se zvýšeným fluencem Au-iontů. Optická charakterizace Au-implantovaných a žíhaných nanopilárů provedená pomocí fotoluminiscence (PL) a difuzně-reflexní spektroskopie (DRS) prokázala aktivitu povrchové plasmonové rezonance (SPR) vložených Au NP. SPR-enhanced rozptyl a PL emise pozorované ve spektrálním rozsahu 500-650 nm jsou připisovány Au NP nebo složitějším Au-klastrům. Kromě toho bylo zjištěno, že elipsometrická měření extinkčního koeficientu dobře potvrzují výsledky z DRS, což ukazuje na zvýšení účinku SPR se zvýšením fluence Au-iontů a po následném žíhání

Chlorine doping of MoSe2flakes by ion implantation

Funding Information: Support by the Ion Beam Center (IBC) at HZDR is gratefully acknowledged. We would like to thank Mr Scheumann for the Au-coating of the samples, Mrs Aniol for the measurements with a stylus profilometer, and Mrs Kunz for TEM specimen preparation. The funding of TEM Talos by the German Federal Ministry of Education of Research (BMBF), Grant No. 03SF0451, in the framework of HEMCP is gratefully acknowledged. A.V. K. acknowledges financial support from the DFG, project KR 4866/2-1. The authors thank the HZDR Computing Center, PRACE (HLRS, Stuttgart, Germany, Project ID: 2018184458), and TU Dresden Cluster “Taurus” for generous grants of CPU time. Publisher Copyright: © The Royal Society of Chemistry. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.The efficient integration of transition metal dichalcogenides (TMDs) into the current electronic device technology requires mastering the techniques of effective tuning of their optoelectronic properties. Specifically, controllable doping is essential. For conventional bulk semiconductors, ion implantation is the most developed method offering stable and tunable doping. In this work, we demonstrate n-type doping in MoSe2 flakes realized by low-energy ion implantation of Cl+ ions followed by millisecond-range flash lamp annealing (FLA). We further show that FLA for 3 ms with a peak temperature of about 1000 °C is enough to recrystallize implanted MoSe2. The Cl distribution in few-layer-thick MoSe2 is measured by secondary ion mass spectrometry. An increase in the electron concentration with increasing Cl fluence is determined from the softening and red shift of the Raman-active A1g phonon mode due to the Fano effect. The electrical measurements confirm the n-type doping of Cl-implanted MoSe2. A comparison of the results of our density functional theory calculations and experimental temperature-dependent micro-Raman spectroscopy data indicates that Cl atoms are incorporated into the atomic network of MoSe2 as substitutional donor impurities. This journal isPeer reviewe