Atomic resolution imaging is demonstrated using a hybrid scanning tunneling/near-field microwave microscope (microwave-STM). The microwave channels of the microscope correspond to the resonant frequency and quality factor of a coaxial microwave resonator, which is built in to the STM scan head and coupled to the probe tip. We find that when the tip-sample distance is within the tunneling regime, we obtain atomic resolution images using the microwave channels of the microwave-STM. We attribute the atomic contrast in the microwave channels to GHz frequency current through the tip-sample tunnel junction. Images of the surfaces of HOPG and Au(111) are presented.
We report quantitative measurements of nanoscale permittivity and conductivity using tuning-fork (TF) based microwave impedance microscopy (MIM). The system is operated under the driving amplitude modulation mode, which ensures satisfactory feedback stability on samples with rough surfaces. The demodulated MIM signals on a series of bulk dielectrics are in good agreement with results simulated by finite-element analysis. Using the TF-MIM, we have visualized the evolution of nanoscale conductance on back-gated $MoS_2$ field effect transistors and the results are consistent with the transport da…
We have designed and built a near-field scanning microwave microscope, which has been used to measure the local microwave response and the local density-of-states (LDOS) in the area including the boundary between the gold deposited and the non-deposited region on highly-orientated pyrolytic graphite at a frequency of about 7.3 GHz. We have succeeded in measuring the spatial variation of both the LDOS and the surface resistance. It can be observed that the surface resistance in gold deposited region with the metallic tunneling spectra is smaller than that in the non-deposited region with the U-…
Molecular and atomic imaging required the development of electron and scanning probe microscopies to surpass the physical limits dictated by diffraction. Nano-infrared experiments and pico-cavity tip-enhanced Raman spectroscopy imaging later demonstrated that radiation in the visible range can surpass this limit by using scanning probe tips to access the near-field regime. Here we show that ultimate resolution can be obtained by using scanning microwave imaging microscopy to reveal structures with feature sizes down to 1~nm using a radiation of 0.1~m in wavelength. As a test material we use tw…
Elastic waves propagating in piezoelectric materials are accompanied by a time-varying electric potential, which is of critical importance for acousto-electronic applications. The spatial mapping of such a potential at microwave frequencies is challenging since the characteristic length scale is determined by the acoustic wavelength of several micrometers. In this work, we report the visualization of surface acoustic waves (SAWs) on ferroelectric samples by transmission-mode microwave impedance microscopy (T-MIM). The SAW potential launched by the interdigital transducer is detected by the tip…
This letter reports measurements of microwave (up to 4.5 GHz) detection in metallic single-walled carbon nanotubes. The measured voltage responsivity was found to be 114 V/W at 77K. We also demonstrated heterodyne detection at 1 GHz. The detection mechanism can be explained based on standard microwave detector theory and the nonlinearity of the DC IV-curve. We discuss the possible causes of this nonlinearity. While the frequency response is limited by circuit parasitics in this measurement, we discuss evidence that indicates that the effect is much faster and that applications of carbon nanotu…
The microwave properties of nano-scale structures are important in a wide variety of applications in quantum technology. Here we describe a low-power cryogenic near-field scanning microwave microscope (NSMM) which maintains nano-scale dielectric contrast down to the single microwave photon regime, up to $10^{9}$ times lower power than in typical NSMMs. We discuss the remaining challenges towards developing nano-scale NSMM for quantum coherent interaction with two-level systems as an enabling tool for the development of quantum technologies in the microwave regime.
Two-dimensional heterostructures with layers of slightly different lattice vectors exhibit a new periodic structure known as moire lattices. Moire lattice formation provides a powerful new way to engineer the electronic structure of two-dimensional materials for realizing novel correlated and topological phenomena. In addition, superstructures of moire lattices can emerge from multiple misaligned lattice vectors or inhomogeneous strain distribution, which offers an extra degree of freedom in the electronic band structure design. High-resolution imaging of the moire lattices and superstructures…
We measure the small signal, 1 GHz source-drain dynamical conductance of a back-gated single-walled carbon nanotube field effect transistor at both low and high dc bias voltages. At all bias voltages, the intrinsic device dynamical conductance at 1 GHz is identical to the low frequency dynamical conductance, consistent with the prediction of a cutoff frequency much higher than 1 GHz. This work represents a significant step towards a full characterization of a nanotube transistor for RF and microwave amplifiers.
We have studied acoustic topological edge modes in a honeycomb phononic crystal composed of metallic nano-pillars on a LiNbO$_3$ substrate. Acoustic band calculations show that the topological surface acoustic wave (SAW) mode inhabits the edge of the honeycomb phononic crystal in spite of the hybridization with the internal acoustic modes of the substrate. Pulse-type microwave impedance microscopy realized clear visualization of the gigahertz topological edge mode between two mutually inverted topological phononic crystals. A frequency-dependent image showed that the edge mode evolves as the b…
The ability to create time-dependent magnetic fields of controlled polarization is essential for many experiments with magnetic resonance. We describe a microstrip circuit that allows us to generate strong magnetic field at microwave frequencies with arbitrary adjusted polarization. The circuit performance is demonstrated by applying it to an optically detected magnetic resonance and Rabi nutation experiments in nitrogen-vacancy color centers in diamond. Thanks to high efficiency of the proposed microstrip circuit and degree of circular polarization of 85% it is possible to address the specifi…
Heating of black-Si by microwaves at 2.45 GHz: effect of nano-needle orientation
The Institute of Science Tokyo（东京科学大学）；Swinburne University of Technology（斯威本科技大学）；Melbourne Center for Nanofabrication (MCN)（墨尔本纳米制造中心）；Vilnius University（维尔纽斯大学）；Institute of Innovative Research, Institute of Science Tokyo（东京科学大学创新研究院）
We present a scanning transmission x-ray microscopy setup combined with a novel microwave synchronization scheme in order to study high frequency magnetization dynamics at synchrotron light sources. The sensitivity necessary to detect small changes of the magnetization on short time scales and nanometer spatial dimensions is achieved by combination of the developed excitation mechanism with a single photon counting electronics that is locked to the synchrotron operation frequency. The required mechanical stability is achieved by a compact design of the microscope. Our instrument is capable of …
We demonstrate imaging using scanning microwave microscopy (SMM) of vital mitochondria in respiration buffer. The mitochondria are isolated from cultured HeLa cells and tethered to a solid graphene support. The mitochondria are kept vital (alive) using a respiration buffer, which provides nutrients to sustain the Krebs cycle. We verify that the mitochondria are "alive" by measuring the membrane potential using a voltage sensitive fluorescent dye (TMRE). The organelles are measured capacitively at 7 GHz. Several technical advances are demonstrated which enable this work: 1) The SMM operates in …
Using the extensively studied V2O3 as a prototype system, we investigate the role of percolation in metal-insulator transition (MIT). We apply scanning microwave impedance microscopy to directly determine the metallic phase fraction p and relate it to the macroscopic conductance G, which shows a sudden jump when p reaches the percolation threshold. Interestingly, the conductance G exhibits a hysteretic behavior against p, suggesting two different percolating processes upon cooling and warming. Based on our image analysis and model simulation, we ascribe such hysteretic behavior to different do…
Conventional quantum transport methods can provide quantitative information on spin, orbital, and valley states in quantum dots, but often lack spatial resolution. Scanning tunneling microscopy, on the other hand, provides exquisite spatial resolution of the local electronic density of states, but often at the expense of speed. Working to combine the spatial resolution and energy sensitivity of scanning probe microscopy with the speed of microwave measurements, we couple a metallic probe tip to a Si/SiGe double quantum dot that is integrated with a local charge detector. We first demonstrate t…
We have developed metal-oxide graphene field-effect transistors (MOGFETs) on sapphire substrates working at microwave frequencies. For monolayers, we obtain a transit frequency up to ~ 80 GHz for a gate length of 200 nm, and a power gain maximum frequency of about ~ 3 GHz for this specific sample. Given the strongly reduced charge noise for nanostructures on sapphire, the high stability and high performance of this material at low temperature, our MOGFETs on sapphire are well suited for a cryogenic broadband low-noise amplifier.
We report on the on-chip detection of microwaves in the frequency range around 100GHz. For the purpose of detection, we employ a discrete transport channel triggered in a superconducting single-electron transistor by photon-assisted tunneling of quasiparticles. The technique is successfully applied to observe the spectrum of the dressed states of a model cQED system consisting of a superconducting coplanar resonator coupled to a quantum Josephson oscillator. The dressed states appear as typical resonance anticrossing exhibiting, in our case, an expectedly wide frequency splitting corresponding…
Dielectric measurements on insulating materials at cryogenic temperatures can be challenging, depending on the frequency and temperature ranges of interest. We present a technique to study the dielectric properties of bulk dielectrics at GHz frequencies. A superconducting coplanar Nb resonator is deposited directly on the material of interest, and this resonator is then probed in distant-flip-chip geometry with a microwave feedline on a separate chip. Evaluating several harmonics of the resonator gives access to various probing frequencies, in the present studies up to 20 GHz. We demonstrate t…
Few-layer phosphorene MOSFETs with 0.3-um-long gate and 15-nm-thick Al2O3 gate insulator was found to exhibit a forward-current cutoff frequency of 2 GHz and a maximum oscillation frequency of 8 GHz after de-embedding for the parasitic capacitance associated mainly with the relatively large probe pads. The gate lag and drain lag of the transistor was found to be on the order of 1 us or less, which is consistent with the lack of hysteresis, carrier freeze-out or persistent photoconductivity in DC characteristics. These results confirm that the phosphorene MOSFET can be a viable microwave transi…
We study the magnetoresistance of an ultrahigh mobility GaAs/AlGaAs two-dimensional electron sample in a weak magnetic field under low-frequency (f < 20 GHz) microwave (MW) irradiation. We observe that with decreasing MW frequency, microwave induced resistance oscillations (MIRO) damp and multi-photon processes become dominant. At very low MW frequency (f < 4 GHz), MIRO disappears gradually and a new SdH-like oscillation develops. The analysis indicates that the new oscillation may originate from alternating Hall-field induced resistance oscillations (ac-HIRO), or can be viewed as a multi-phot…
We discuss the effects of gigahertz photon irradiation on a degenerately phosphorous-doped silicon quantum dot, in particular, the creation of voltage offsets on gate leads and the tunneling of one or two electrons via Coulomb blockade lifting at 4.2K. A semi-analytical model is derived that explains the main features observed experimentally. Ultimately both effects may provide an efficient way to optically control and operate electrically isolated structures by microwave pulses. In quantum computing architectures, these results may lead to the use of microwave multiplexing to manipulate quant…
We measure the longitudinal conductivity $σ_{xx}$ at frequencies $1.246 {\rm GHz} \le f \le 10.05$ GHz over a range of temperatures $235 {\rm mK} \le T \le 4.2$ K with particular emphasis on the Quantum Hall plateaus. We find that $Re(σ_{xx})$ scales linearly with frequency for a range of magnetic field around the center of the plateaus, i.e. where $σ_{xx}(ω) \gg σ_{xx}^{DC}$. The width of this scaling region decreases with higher temperature and vanishes by 1.2 K altogether. Comparison between localization length determined from $σ_{xx}(ω)$ and DC measurements on the same wafer show good agre…
The ability to achieve strong-coupling has made cavity-magnon systems an exciting platform for the development of hybrid quantum systems and the investigation of fundamental problems in physics. Unfortunately, current experimental realizations are constrained to operate at a single frequency, defined by the geometry of the microwave cavity. In this article we realize a highly-tunable, cryogenic, microwave cavity strongly coupled to magnetic spins. The cavity can be tuned in situ by up to 1.5 GHz, approximately 15% of its original 10 GHz resonance frequency. Moreover, this system remains within…
The bulk electronic properties of compensated topological insulators are strongly affected by the self-organized formation of charge puddles at low temperature, but their response in the microwave frequency range is little studied. We employed broadband impedance spectroscopy up to 5 GHz to address the ac transport properties of well-compensated BiSbTeSe2, where charge puddles are known to form as metallic entities embedded in an insulating host. It turns out that the average puddle size sets the characteristic frequency cut-off in the GHz range, across which the insulating dc behavior is sepa…
We report on a planar microwave resonator providing arbitrarily polarized oscillating magnetic fields that enable selective excitation of the electronic spins of nitrogen-vacancy (NV) centers in diamond. The polarization plane is parallel to the surface of diamond, which makes the resonator fully compatible with (111)-oriented diamond. The field distribution is spatially uniform in a circular area with a diameter of 4 mm, and a near-perfect circular polarization is achieved. We also demonstrate that the original resonance frequency of 2.8 GHz can be varied in the range of 2-3.2 GHz by introduc…
Microwave photons inside lattices of coupled resonators and superconducting qubits can exhibit surprising matter-like behavior. Realizing such open-system quantum simulators presents an experimental challenge and requires new tools and measurement techniques. Here, we introduce Scanning Defect Microscopy as one such tool and illustrate its use in mapping the normal-mode structure of microwave photons inside a 49-site Kagome lattice of coplanar waveguide resonators. Scanning is accomplished by moving a probe equipped with a sapphire tip across the lattice. This locally perturbs resonator freque…
