Cheng Ji

 Collaborated across teams to scale superconducting quantum technologies for semiconductor applications  Developed fabrication process for superconducting qubits and circuits on industry-standard 300 mm wafers  Implemented in-line metrology for Aluminum thin film grain size with industry-standard SEMVision G7.  Developed machine learning image analysis algorithm for crystal grain statistics with 90% accuracy.  Optimized the superconducting co-planar waveguide and resonator performance with Ansys HFSS;  Designed defect analysis experiment for Al/AlOx/Al Josephson Junctions.

I am doing my Ph.D. research on the single Er ion quantum memories at Argonne National Lab, advised by Prof. Supratik Guha and Prof. Alan Dibos. My research mainly includes: - Silicon photonics simulation, design and fabrication - Erbium quantum memory development - Process development and integrations for Er doped TiO2 on SOI based photonics circuits - Building and programming optical setup - Characterization of Erbium emission properties at telecom wavelength - Characterization of Erbium emitter coupled with nanophotonic cavities - Single photon emission analysis - Design and fabrication the optical coupling from on-chip waveguide to lens fiber - Thin film characterization of Er doped oxide materials - Develop atomic layer deposition recipes for Er doped TiO2 thin film and the CMOS foundry integration - Quantum electrodynamics effect of Er emitters in nanophotonic cavities Other projects: - Novel circuit design and fabrication for single photon detectors, realizing a 10x efficiency improvement - Mechanically robust broad band anti-reflective coatings for display - Novel memristors oxide process development for neuromorphic computing

Use Comsol to simulation topological behavior in photonics and phononic lattice.

I worked on my graduation thesis project on Molecular Beam Epitaxy Growth and Characterization of InAs/GaSb Double Quantum Well, under the supervision and guidance of Professor Jianjun Zhang, a scientist from the Institute of Physics, CAS, with a research focus on silicon-based nanometer devices. I have learned to carry out film material growth of molecular beam epitaxy (MBE) and fabricate and characterize suitable devices. I have been familiar with the MBE system, including the RHEED monitoring growthI worked on my graduation thesis project on Molecular Beam Epitaxy Growth and Characterization of InAs/GaSb Double Quantum Well, under the supervision and guidance of Professor Jianjun Zhang, a scientist from the Institute of Physics, CAS, with a research focus on silicon-based nanometer devices. I have learned to carry out film material growth of molecular beam epitaxy (MBE) and fabricate and characterize suitable devices. I have been familiar with the MBE system, including the RHEED monitoring growth process and the way to measure the beam equivalent pressure. Meanwhile, I proposed new growth recipe of AlSb/InAs/GaSb/AlSb double quantum wells to get high carrier mobility and concentration for future possible applications in topological quantum computing devices. process and the way to measure the beam equivalent pressure. Meanwhile, I proposed new growth recipe of AlSb/InAs/GaSb/AlSb double quantum wells to get high carrier mobility and concentration for future possible applications in topological quantum computing devices.

In summer 2018, I participated in a project at Technical Institute of Physics and Chemistry (IPC) with the goal to explore The Construction of Quantum Tunneling Junction with Liquid Metal and successfully came up with two possible constructing methods. This research was a bold trial to explore flexible quantum computation with new liquid metal, specifically, eutectic gallium-indium (EGaIn). I conducted a concrete investigation for the classic solid-state quantum tunneling device like Josephson Junctions and attempted to design the soft junction in the air, vacuum, and liquid environments respectively, with hope to tackle the thermal expansion of liquid metal and the dielectric’s breakdown. With my continual efforts in investigating related literature and observing the experimental condition, I proposed to make use of CVD 2D insulator catalyzed by EGaIn and designed the instruments accordingly. Besides, I operated precise instrument like Scanning Electron Microscope and X-Ray Diffraction in measuring the insulation properties. Meanwhile, I participated in another work about EGaIn Catalyzed Rapid Synthesis of Hydrogen Bronze Structures in IPC with the objective of doping a large number of Hydrogen atoms into WO3 rapidly in room temperature with Liquid Metal reaction enhancement. In the research, I independently purchased the instruments and constructed the platform and successfully completed the chemical potential measurements of tungsten and liquid metals in acid solutions. Besides, I also exerted the bandgap calculation on samples with different Hydrogen concentration, from the data acquired by Ultraviolet-visible Spectroscopy. The works are included in the article Liquid Metals Inspired Electrochemical-Chromic Function: One-Step Synthesis of the Hydrogen Bronze Structures at Room Temperature, which has been published on ACS Omega.

I followed Professor Alex Zettl on the project Effects on Electrical Properties Imposed by Lattice Defects in the Heterostructures of MoS2 and WSe2 Monolayers in UC Berkeley. This exposure to start-of-the-art research, which is meaningful for improving the 2D-device performance, has strengthened my resolution to further in physics by elevating my understanding regarding low dimensional physics. At Berkeley, I was mainly engaged in building p-n junction structure of n-type MoS2 and p-type WSe2 on 426nm SiO2 and overlaying 2-5nm h-BN as insulation protection. By collaborating with Aiming Yan, a post-doctoral researcher at Berkeley, I exercised PC/PDMS transfer technique and introduced lattice defects by TEM scanning on GaN substrate so as to study the impact of lattice defects on carrier mobility. To eradicate the interference caused by impurities and bubbles in the heterojunction to TEM imaging, I independently did experiments by changing temperature when transferring 2D materials, PC’s solution concentration and annealing conditions. Trials were also exerted by utilizing AFM pinhead to clean the interface of the heterojunction. This research has rewarded me with in-depth understanding and mastery of complicated experimental procedures, including plasma activation of silicon surface, Chemical Vapor Deposition (CVD), as well as preparation of polymer compounds, which will definitely facilitate my further lab experimentations. Additionally, the discussion with the senior undergraduate researcher Salman Kahn on the research regarding two-dimensional device physics, I gained further visions of the graphene applications in electronic devices and the great potentials for transition metal dichalcogenides.

Under the guidance of Prof. Yinghui Wang(王英辉), I gleaned information regarding plasma applications and vacuum technology and conducted a series of experiments, such as clean the surface of silicon and gold with plasma, to test the effect of plasma. In the internship, I concluded that positive result: the plasma can clean the surface effectively and activate the surface by making the silicon dioxide surface easier to bond with other materials throught the experiments.

Courses: Microfabrication Technology- A+ Introduction to the Communication Network - A Introduction to the Plasma Physics - A In Microfabrication Technology, apart from studying the theoretical methods of analyzing semiconductor fabrication process like CVD, Ion Implantation and dopant diffusion, in the ultra-clean room, I operated the instruments like Spin Coater and Oxidation Furnace and exercised standard wafer cleaning with chemicals.