About

Wilson Ho is the Donald Bren Professor and Distinguished Professor of Physics and Astronomy & Chemistry at the University of California, Irvine. He received his B.S. and M.S. degrees in chemistry from the California Institute of Technology in 1975 and his Ph.D. in physics from the University of Pennsylvania in 1979. His professional experience includes a year at the AT&T Bell Laboratories as a Member of the Technical Staff and faculty positions at Cornell University before joining UCI in 2000. His research focuses on nanoscale chemical and physical phenomena, emphasizing probing the basic properties of single atoms and molecules in their nano-environment on solid surfaces. The goal is to obtain detailed descriptions of single atoms and molecules to understand chemical and physical processes at surfaces and properties of nanostructured condensed matter and molecular materials. His work involves understanding matter and its interactions at the atomic and molecular level, controlling chemistry at the level of individual atoms and molecules, and studying magnetism down to single atoms. He extensively utilizes the scanning tunneling microscope (STM) as a tool for visualizing, manipulating, and spectroscopically characterizing individual atoms and molecules, effectively functioning as a nanoreactor. His contributions include demonstrating chemical analysis with STM using inelastic electron tunneling spectroscopy (IETS), achieving sensitivity at the level of a single bond, and enabling spatially resolved vibrational intensity measurements with sub-Angstrom resolution. His research encompasses a wide range of problems such as intramolecular energy transfer, energy dissipation during bond breaking, chemical identification, structural determination of reactants and products, orbital-specific chemistry, molecular electronics, diffusion of single hydrogen atoms, and fundamental molecular motions. His work also extends to time-resolved phenomena with femtosecond lasers, atomically resolved imaging, spectroscopy, dynamics, and chemistry with low-temperature STM, as well as nonequilibrium materials synthesis and device fabrication.

Research topics

• Materials science
• Chemistry
• Atomic physics
• Molecular physics
• Physics

Selected publications

• Assessing the Operating Characteristics of an Ion-Milled Phonon-Mediated Quantum Parity Detector

  IEEE Transactions on Applied Superconductivity · 2026-04-29

  articleOpen access

  Phonon sensitive superconducting qubits promise to provide sub-eV energy deposit thresholds, useful for future rare-event experiments looking for interactions from dark matter and neutrinos. We detail here engineering results from a Quantum Parity Detector (QPDs), one of a class of phonon sensitive qubits, and, as a first measurement, show that this device has a quiescent quasiparticle density of $1.8 \pm 0.8 μ\mathrm{m}^{-3}$, in line with expectation. We also outline an argon ion-mill process for multi-step Josephson Junction fabrication, expanding the sparse literature on this topic, which proves useful in avoiding secondary parasitic junctions.

  PublisherOA PDFDOI

• High-efficiency Pt75Au25-based spintronic terahertz emitters

  Applied Physics Letters · 2026-02-23

  articleOpen access

  Spintronic terahertz emitters (STEs) generate broadband THz radiation via ultrafast spin–charge conversion in magnetic multilayers, offering spectral coverage beyond that of photoconductive antennas and nonlinear optical crystals. Here, we demonstrate STEs based on a PtxAu100−x alloy that achieve significantly higher THz output power than widely used Pt-based devices. Alloy composition and layer thickness tuning yield Pt75Au25 as the optimal alloy, providing a 30% increase in THz power in CoFeB/Pt75Au25 bilayer STEs compared to the optimized CoFeB/Pt reference STE. In W/CoFeB/Pt75Au25 trilayer STEs, we observe a 10% higher THz power than in the optimized W/CoFeB/Pt trilayer. The STE efficiency is reduced upon annealing for both Pt75Au25- and Pt-based STEs due to the formation of interfacial alloys. Our results establish Pt75Au25 as a promising platform for high-performance STEs, where its giant spin Hall effect significantly enhances efficiency over conventional Pt-based devices.

  PublisherOA PDFDOI

• Biobased Epoxy Amine Primers for Corrosion Protection of Steel & Aluminum Alloys

  2025-04-06

  article

  Abstract The development of environmentally friendly cure chemistries which can be used to make polymers is a major area of focus in the polymer industry [1]. One area of particular interest to the DoD and Army Corps of Engineers is the development of biobased epoxies and amines which can be used as an alternative to petrochemical based building blocks to make biobased epoxy-amine coatings for the corrosion protection of various substrates. In this presentation, the corrosion performance of epoxy-amine primers under development is assessed by a combination of electrochemical measurements and accelerated corrosion tests and benchmarked against petrochemical based coating technologies. Among different biobased technologies tested, epoxy cured with biobased amine (difuran diamine) showed good performance in both corrosion testing and electrochemical measurements.

  PublisherDOI

• Quantum Stochastic Rectification in a Single Molecule

  Physical Review Letters · 2025-06-14 · 2 citations

  articleSenior author

  Quantum stochastic rectification arises from the dc response of a system subjected to both quantum noise and a small, periodic sinusoidal voltage modulation. In this Letter, we demonstrate quantum stochastic rectification by using inelastic electron tunneling spectroscopy with a scanning tunneling microscope to monitor the conformational switching of a single pyrrolidine molecule adsorbed on a Cu(001) surface. By applying quasistatic and nonequilibrium approximations, we elucidate the underlying dynamic response mechanisms. Additionally, we establish a quantitative relationship between the critical driving frequency in rectification measurements and the system's relaxation time, facilitating the measurement of rapid relaxation rates in single molecules.

  PublisherDOI

• Differences in Benzene Concentration Across Packaging Types During Normal Use of Benzoyl Peroxide Products

  Journal of Cosmetic Dermatology · 2025-09-22

  articleOpen access

  Benzoyl peroxide (BPO) is a common treatment for acne, but concerns have been raised about the potential formation of benzene in BPO products under varying environmental conditions [1]. This issue has gained attention in Taiwan, where local media have reported on benzene-related risks, raising public concern. In Taiwanese medical institutes, especially in clinics, patients are given tubes or dispensed ointment boxes. We hypothesized that differences in benzoyl peroxide packaging types, specifically tubes and dispensed ointment boxes, may influence benzene accumulation due to varying levels of air exposure. Previous studies suggest that high temperatures may promote benzene formation in benzoyl peroxide products, potentially increasing health risks due to benzene's known carcinogenicity [2]. Analysis of FAERS data identified skin reactions like irritation but no strong evidence of malignancy, reinforcing the safety of routine use [3]. However, there is a significant need to let people understand about the risks of benzene formation. Research also suggests that adjusting formulations, such as incorporating antioxidants, can significantly lower benzene levels in BPO products, providing a proactive solution for manufacturers to adopt [4]. This experiment aimed to evaluate benzene concentrations in benzoyl peroxide (BPO) products under two temperature conditions—room temperature (approximately 25°C) and high temperature (40°C–70°C)—as the primary variable, with air exposure as the secondary variable. The high-temperature range was selected to simulate conditions such as a car interior in Taiwan during summer, based on environmental studies. Benzene concentrations were measured in Aczo Gel 50 mg/g (Sinphar) packaged in tubes (10 g) and dispensed ointment boxes (5 g) at room and high temperatures after the 2nd, 4th, and 6th weeks. The high-temperature group was placed in a heater set to 40°C–70°C. All containers were opened for 10 s twice-daily to mimic normal use (twice-daily application). Samples were analyzed in a private laboratory using established gas chromatography methods [1]. The final data of the experiment are shown in the table. As the result demonstrated, the concentration of benzene will increase as temperature was higher accordingly in the two groups. In fact, the concentration of benzene shows higher in the tube than the dispensed ointment box (Table). Furthermore, we speculated that the difference in contact area with air influenced the evaporation of benzene, as larger surface area increases the likelihood of release. In addition, we found that in the 6th week, it shows that the benzene production of BPO enormously decreased, it might suggest that the chemical reaction of benzene production had reached the peak. Unfortunately, the sample is not enough, which means it might require more examples to support this hypothesis. Given these findings, ointment boxes might be a safer choice for patients due to lower benzene production compared with tubes, aligning with Taiwan's dispensing preferences. For all intents and purposes, in our perspective, we think using dispensed ointment boxes provides a safer environment to the patients, due to the lower production of benzene. The authors have nothing to report. The authors declare no conflicts of interest. The authors have nothing to report.

  PublisherOA PDFDOI

• Origin of photoinduced DC current and two-level population dynamics in a single molecule

  Science Advances · 2024-01-31 · 3 citations

  articleOpen accessSenior authorCorresponding

  Studying the photoinduced changes of materials with atomic-scale spatial resolution can provide a fundamental understanding of light-matter interaction. A long-standing impediment has been the detrimental thermal effects on the stability of the tunneling gap from intensity-modulated laser irradiation of the scanning tunneling microscope junction. Photoinduced DC current transduces photons to an electric current and is widely applied in optoelectronics as switches and signal transmission. Our results revealed the origin of the light-induced DC current and related it to the two-level population dynamics and related nonlinearity in the conductance of a single molecule. Here, we compensated for the near-visible laser-induced thermal effects to demonstrate photoinduced DC current spectroscopy and microscopy and to observe the persistent photoconductivity of a two-level pyrrolidine molecule. The methodology can be generally applied to the coupling of light to scan probes to investigate light-matter interactions at the atomic scale.

  PublisherOA PDFDOI

• Structure and Topography of Facial Branchiomotor Neuron Dendrites in Larval Zebrafish ( <i>Danio rerio</i> )

  The Journal of Comparative Neurology · 2024-11-01

  articleOpen accessSenior author

  Motor circuits in the vertebrate hindbrain need to become functional early in development. What are the fundamental mechanisms that establish early synaptic inputs to motor neurons? Previous evidence is consistent with the hypothesis that motor neuron dendrite positioning serves a causal role in early spinal motor circuit development, with initial connectivity determined by the overlap between premotor axons and motor neuron dendrites (perhaps without the need for molecular recognition). Does motor neuron dendrite topography serve a similar role in the hindbrain? In the current study, we provide the first quantitative analysis of the dendrites of facial branchiomotor neurons (FBMNs) in larval zebrafish. We previously demonstrated that FBMNs exhibit functional topography along the dorsoventral axis, with the most ventral cell bodies most likely to exhibit early rhythmic activity-suggesting that FBMNs with ventral cell bodies are most likely to receive inputs from premotor neurons carrying rhythmic respiratory signals. We hypothesized that this functional topography can be explained by differences in dendrite positioning, giving ventral FBMNs preferential access to premotor axons carrying rhythmic signals. If this hypothesis is true, we predicted that FBMN cell body position would be correlated with dendrite position along the dorsoventral axis. To test this prediction, we used single-cell labeling to trace the dendritic arbors of FBMNs in larval zebrafish at 5-days post-fertilization (dpf). FBMN dendrites varied in complexity, and this variation could not be attributed to differences in the relative age of neurons. Most dendrites grew caudally, laterally, and ventrally from the cell body-though FBMN dendrites could extend their dendrites dorsally. Across our sample, FBMN cell body position correlated with dendrite position along the dorsoventral axis, consistent with our hypothesis that differences in dendrite positioning serve as the substrate for differences in activity patterns across neurons. Future studies will build on this foundational data, testing additional predictions of the central hypothesis-to further investigate the mechanisms of early motor circuit development.

  PublisherOA PDFDOI

• New applications on multi-beam mask writers to enable mask-making in 3nm and beyond

  2024-11-26 · 2 citations

  article

  To meet the demanding requirements for pattern fidelity, critical dimension and placement errors on advanced masks, the use of multi-beam mask writers together with using low sensitivity resists became necessary and inevitable. To reach the targeted throughput on such low sensitivity resists, an increase of the beam current is necessary which results in two problems. Worse beam stability control increases the risks of pattern errors and thus leads to higher yield loss. In addition, stronger resist charging and thermal effects also result in more unpredictable displacement errors which in turn make overlay control much more difficult. Here we present a new method that utilizes machine learning to detect tool abnormalities and trigger immediate exposure interruption which significantly reduces the mask yield loss. To reduce and compensate stronger charging and thermal effects from a higher beam current, we introduce hardware modifications and software corrections as well as an exposure sequence optimization that in combination minimize the yield loss and overlay problems and enable mask making in 3nm and beyond.

  PublisherDOI

• 3D Radon transformation with axis dependent curvature

  2024-07-24

  article

  Radon transformation is a popular tool in seismic data processing, imaging, and analysis. The Radon domain is used for deconvolution, multiple suppression, noise muting, and interpolation for pre-processing. Radon transformed data are also used for beam and plane-wave imaging. Data with various curvature are separated in the transformed domain which is a powerful tool for seismic processing and muting. Commonly used methods are linear, parabolic, and hyperbolic. Parabolic and hyperbolic methods have proven to be very useful for normal moveout-corrected data where only flat and curved events are present. Linear Radon is useful for deconvolution, de-multiple and noise muting. Seismic data may have different curvatures along different axes; to handle this issue we propose a mixed curvature Radon transformation, which applies linear and parabolic transformations in the X and Y directions separately or vice versa. We show both synthetic and real data examples to demonstrate that our proposed method is a good alternative for input data with mixed curvatures.

  PublisherDOI

• Mechanisms Underlying a Quantum Superposition Microscope Based on THz-Driven Coherent Oscillations in a Two-Level Molecular Sensor

  Physical Review Letters · 2024-02-16 · 6 citations

  articleOpen accessSenior author

  We report pump-probe measurements of a hydrogen molecule (H_{2}) in the tunnel junction of a scanning tunneling microscope coupled to ultrashort terahertz (THz) pulses. The coherent oscillation of the THz-induced dc tunneling current at a frequency of ∼0.5 THz fingerprints the absorption by H_{2} as a two-level system (TLS). Two components of the oscillatory signal are observed and point to both photon and field aspects of the THz pulses. A few loosely bound states with similar energies for the upper state of the TLS are evidenced by the coherent revival of oscillatory signal. Furthermore, the comparison of spectroscopic features of H_{2} with different tips provides an understanding of the TLS for H_{2}.

  PublisherOA PDFDOI

Recent grants

• Atomic Scale Chemistry

  NSF · $850k · 2006–2011

• Multidimensional Spectromicroscopy of Molecular Magnetism

  NSF · $550k · 2018–2022

• Four-Dimensional Probe of Electron Spin-Spin Coupling

  NSF · $590k · 2014–2018

• Imaging, Manipulation, and Control of Molecular Quantum Systems

  NSF · $420k · 2019–2022

Frequent coauthors

• Ruqian Wu

  25 shared

• Z. Ying

  Hainan Medical University

  22 shared

• Joseph A. Stroscio

  21 shared

• Lincoln J. Lauhon

  19 shared

• Gregory Czap

  18 shared

• Lee J. Richter

  National Institute of Standards and Technology

  18 shared

• S. A. Ustin

  Fraunhofer Project Centre Wolfsburg

  17 shared

• Shaowei Li

  Beijing University of Technology

  16 shared

Education

• Ph.D., Physics

  University of Pennsylvania

  1979

• B.S., Chemistry

  California Institute of Technology

  1975

• M.S., Chemistry

  California Institute of Technology

  1975