Jinjin Li

Guizhou Normal University · School of Psychology

This work proposes a balanced segmentation scheme to improve microwave transmission and develops a 2 V programmable Josephson junction array using double-stacked superconductor-normal-metal-superconductor Josephson junctions. The junction numbers of the sub-Josephson arrays are divided into a ternary sequence. The least significant bit is one stack...

With the increase in integration and the layers of superconducting electronics circuits, molybdenum (Mo)-based films become attractive resistive and inductive functional components because of the large kinetic inductance with the deep magnetic field penetration depth. A DC magnetron sputtering technology is used to fabricate Mo and MoNx films. The...

The outbreak of COVID-19 has led to a global health crisis and caused huge emotional swings. However, the positive emotional expressions, like self-confidence, optimism, and praise, that appear in Chinese social networks are rarely explored by researchers. This study aims to analyze the characteristics of netizens' positive energy expressions and t...

In this study, radio frequency (RF) biased direct current (DC) magnetron sputtering was used to simultaneously improve the surface roughness and superconducting properties of Nb thin films for Josephson circuits application. The surface roughness of the Nb films decreased with an increase in RF powers, whereas the transition temperature, transition...

SiO2 is one of the most widely used dielectric materials in optical and electronic devices. The Josephson voltage standard (JVS) chip fabrication process has rigorous requirements for the deposition temperature and step-coverage profiles of the SiO2 insulation layer. In this study, we deposited high-quality SiO2 insulation films at 60 °C using indu...

Transition-edge sensors (TES) are remarkable superconducting devices for a wide range of radiation detection with the ability of both energy resolution and counting photons. For the detection of single photons at telecom wavelength, optical Ti/Au bilayer TESs are fabricated and characterized. The superconducting transition temperature (Tc) of the T...

Currently, the coronavirus disease 2019 (COVID-19) pandemic experienced by the international community has increased the usage frequency of borderless, highly personalized social media platforms of all age groups. Analyzing and modeling texts sent through social media online can reveal the characteristics of the psychological dynamic state and livi...

Background The COVID-19 has led to unprecedented psychological stress on the general public. However, the associations between media exposure to COVID-19 and acute stress responses have not been explored during the early COVID-19 outbreak in China. Methods An online survey was conducted to investigate the relationships between media exposure to CO...

In this work, the interface composition of the superconducting Ti/PdAu bilayer is tuned by an annealing process in N2 from 100 to 500 °C to control the superconducting transition temperature (Tc). This Ti-PdAu composition layer is characterized with a high-resolution transmission electron microscopy (HRTEM) and energy-dispersive spectrometer (EDS)...

Nano-superconducting quantum interference devices (nano-SQUIDs) with high energy sensitivity and spatial resolution are essential in many applications such as single spin detection, nano-electromechanical vibration detection and microscale magnetic imaging. This paper studies a Dayem-type niobium nano-SQUID using focus ion beam milling technology....

This paper presents a superconducting material based planar broadband 3-way Wilkinson power divider which can be used in the Josephson quantum voltage device for the voltage standards. The 3-way Wilkinson power divider aims to improve the integration of Josephson voltage device compared to the commonly used 2-way power divider. A two-stage /4 secti...

Quantum Hall effect is used to realize resistance standard which is in terms of the Planck constant [Formula: see text] and elementary charge [Formula: see text] in metrology. The quantum Hall resistance devices are fabricated based on two-dimensional electron gas formed in [Formula: see text] as heterostructures. Low-resistance Ohmic contact to th...

Large-scale Josephson junction (JJ) arrays are essential in many applications, especially quantum voltage standards application for which hundreds of thousands of junctions are required to realize a high quantum voltage. For almost all applications, high-quality JJ arrays must be realized in a small chip area. This study proposes vertically quadrup...

We report research on superconducting transition temperature (Tc) tuning and the antireflective layer of NbxSi1-x films that were used as the absorbing layer in inductive superconducting transition edge detectors (ISTED). The Tc of NbxSi1-x film absorber should be tuned to be to the operating temperature range of the readout nano superconducting qu...

The design, fabrication, and the characterization of a 0.5-V Josephson junction array device are presented for the quantum voltage standards in the National Institute of Metrology (NIM) of China. The device consists of four junction arrays, each of which has 1200 3-stacked Nb/Nb x Si 1− x /Nb junctions and an on-chip superconducting microwave circu...

An antireflective layer should be fabricated on the surface of Nb film which was used as the photon energy detection unit in the single photon standard.The spectral refractive index characteristics of Nb films with different thickness made by a magnetron sputter system, SiO2 and SiNx films made by a plasma enhanced chemical vapor deposition system...

Superconducting quantum interference devices (SQUIDs) with 3 μm × 3 μm or 4 μm × 4 μm self-shunted Nb/Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> /Nb Josephson junctions are design...

Magnetron sputtering is an important method in the superconducting thin films deposition. The residual gas inside the vacuum chamber will directly affect the quality of the superconducting films. In this paper, niobium films are deposited by magnetron sputtering under different chamber residual gas conditions. The influence of baking and sputtering...

Two kinds of quantum Hall devices with different working magnetic fields are fabricated and compared with the LEP (Laboratoires d'Electronique Philips) device, which is currently used in the primary resistance standard system of the National Institute of Metrology (NIM) of China. The comparison is made by calibrating the same 1 standard resistor ma...

In this paper we report the progress on single quantum Hall devices for the resistance standards in NIM. We use the NIM-made device and the LEP-made device distributed to NIM by BIPM to calibrate a Tinsley 100 Ω transfer resistor using a cryogenic current comparator (CCC) at the filling factor k=2. The deviations of resistance values from the nomin...

NanoSQUIDs with Dayem nanobridge weak-link junctions were fabricated on single layer niobium film by focus ion beam(FIB) milling. The dimension of the nanobridge is less than 60 nm and the loop scale is from 400×400 nm to 2.5×20 μm. The working temperature range for this device was researched. The voltage-flux transfer properties were measured at d...

Quantum Hall (QH) standard devices based on chemical vapor deposition (CVD) graphene have not shown properties as excellent as the one based on epitaxial graphene on SiC. This is because of the impurity, defects and inhomogeneity. In this paper, we demonstrate the progress on improving the quality of CVD graphene by the surface acidic processing an...

Josephson junction array chips for microvolt applications have been designed and fabricated. A voltage step as small as 1 μV has been observed for a single junction in the array when it is driven by 483.59 MHz microwave. By selecting different parts of the array, it can output a voltage from 1 μV to 256 μV. The flat region of the voltage steps is o...

We report the fabrication and measurement of quantum Hall (QH) array devices based on GaAs/AlGaAs heterostructure in NIM. Three QH arrays, namely 2 Hall bars in series, 2 Hall bars in parallel, and 4 Hall bars in series are demonstrated. The low resolution preliminary measurement results are presented. The present resolution is limited by the measu...

We reported the new design of quantum Hall array resistances. Two resistances, 100 and 1k, were achieved by series and parallel connections of single quantum Hall device based on the AlGaAs/GaAs heterostructure. The relative deviations from the nominal value were-3.42 parts of 108 for both design.

Reactive ion etching (RIE) is a common tool in micro- and nano-scale device fabrication. This paper presents experimental results of using the RIE tool to etch different films in Nb/NbxSi1-x/Nb Josephson junction array fabrication process in NIM.

We report in CPEM 2014 our latest results of the study of single quantum Hall device for the resistance standard in National Institute of Metrology, China (NIM). Experimental results indicate quantized Hall devices with satisfied longitudinal resistance, low contact resistance, and good breakdown current are obtained. Comparison of the quantum Hall...

Large scale single-crystalline graphene was achieved on copper foils with CH4 as the precursor with a sandwich method. With a PMMA-assisted method, single-crystalline graphene was transferred to the marked SiO2/Si substrate. Quantum Hall devices will be fabricated by E-beam lithography and metallization. And, quantum Hall effect will be measured.

Wafer-scale monolayer graphene film was synthesized on Cu foils by chemical vapor deposition in a 3-in thermal furnace. Graphene film was transferred to the surface of SiO2 (300 nm)/Si substrates using a polymer-assisted method. Hall bar structures were fabricated by lithography and E-beam deposition for the electrical property measurement. Perfect...

The core device of Modern programmable Josephson voltage standard is Josephson junction array. The most advantageous Josephson junction array is Nb/Nb xSi 1-x/Nb material array. The advantages of Nb/Nb xSi 1-x/Nb material Josephson junction are that three-layer film production process is simple, Nb and Nb xSi 1-x etching processes are the same and...

Both SF6 and CF4 are plasma chemistries that are often used during dry etching in fabricating the niobium Josephson junctions. This paper presents the preliminary experimental results of using these two etches on etching Nb/NbxSi1-x/Nb Josephson junctions in NIM.

We report in CPEM 2012 the preparation of the micromechanical cleavage (MC) and the chemical vapor deposition (CVD) graphene films and the fabrication of the quantum Hall resistance (QHR) devices on these films. Graphene films are on the SiO2/Si substrates. Spectroscopic Raman analysis indicates monolayer graphene films are obtained. Hall bar struc...