superconducting tunnel junctions in scientific instrumentation AIST - PowerPoint PPT Presentation

New application stages of superconducting tunnel junctions in scientific instrumentation AIST University of Tsukuba RIKEN Masataka Ohkubo, Shigeo Tomita, Toshiyuki Azuma Masahiro Ukibe, Nobuhiro Kim Shigetomo Shiki, Go Fujii, Nobuyuki Zen, Katsutoshi Takahashi 2015/07/22 LTD-16 2015 Grenoble

Background STJ detectors have a long history of more than 40 years. Many applications of STJ detectors have been proposed and some of them were not feasible for practical use as scientific instruments due to a low detection efficiency and a problem of thermal inflow and so on. Improvement of the fabrication technique CRAVITY (Clean room for analog-digital superconductivity ) Original techniques • Planarization process [Caldera process] • oxidation process [Ozone process] Fabrication of advanced superconducting devices A large scale STJ array with high performance (high D E [G1.44], quite • low leakage[G2.4], 3D-STJ[G1.42], SPA-STJ[G1.43]) • Superconducting signal processor (SFQ-TDC) [G2.48] LTD-16 2015 Grenoble 2015/07/22

CRAVITY ： Layout Access to https://unit.aist.go.jp/riif/openi/cravity/en/equipment/2-12expo.html# ● Room1 (Class 100) : Lithography-room （ 90m 2 ） Measurement instrument ・ Single wafer cleaner Process equipment ・ i-line stepper Room 1 ・ Auto or semi coat/develop system Semiauto develop ・ Wafer processor for wet stripping system Auto coat/develop Single wafer system of photoresist cleaner Room 3 Microscopes ・ Wafer surface Wafer processor for Room 2 wet stripping of photoresist TEOS-CVD analyzer Sputter machine for Nb wiring i-line stepper Sputtering machine for ・ Microscopes Nb/Al JJ [Ozone oxidization and mass spectrometer] Multi target Alpha Sputter machine Thin film (6 targets) -step ● Room2 for SiO 2 interlayer Sputter machine stress measurement sputter machine insulation film for NbN/TiN JJ Sputtering machine (Class 1000-10000) For Nb/Al JJ Nano search [Standard type] RIEs CCP type:4,ICP microscpe Alpha-step type :1 :Deposition-room(70m 2 ) Auto and manual Laser prober microscope ・ Sputtering machines for RTA Josephson junction （ Nb/Al,NbN/TiN ） Resistivity Ellipsometer mapping system ・ Dry etching equipments （ RIE, Asher ） CMP process ・ Auto and manual probers equipments ● Utility space (30m 2 ) ・ Thin film stress measurement system ・ Supply equipment of ● Room3 (Class10000) process gases :Deposition-room(100m 2 ) Standard wafer size ・ Vacuum exhaust units ・ TEOS-CVD （ SiO 2 , SiON ） ・ DI-water system at every machine : 3inch ・ CMP process equipments ・ Waste HF tank ・ Nano search microscope LTD-16 2015 Grenoble 2015/07/22

Available technologies at CRAVITY Junction Active layer M9 including JJ and R JC • Nb technology JJ BC M8 SiO 2 RES M7 Main ground plane Main GP and CPL M6 2 nd PTL C5 M5  10-kA/cm 2 advanced process layer M4 1 st PTL C3 M3 layer C2 M2 DC power C1 M1 layer  2.5-kA/cm 2 standard process Si Substrate  Low-leakage(0.1 pA/ m m 2 @200 A/cm 2 ) tunnel junction process V + 14.7 mm • NbN technology 4.7mm RF input  SNS-junction process for 10-K operation 16 Microwave Voltage generator （ 1 V × 2 ） Termination divider area V - • Al technology  Deep sub- μ trilayer-junction process Available electronics at CRAVITY Analog devices: STJ, SQUID, TES, and MKID Digital devices : SFQ circuits, and qubits ISEC 2015 NAGOYA 2015/07/22

Latest fabrication technology Advanced process(ADP ) Nb 9-layer structure Planarization process (Caldera process) Conventional Process ISEC 2015 NAGOYA 2015/07/22

3D wiring for STJ detectors 2D-wiring sparse Filling factor ~ 7% Closed-packed array ~70% 512 pixels ~1.3 mm Sparse array 7% 3D-wiring close-packed 10 mm 10 mm Filling factor ~ 70% JJ size and Pitch : 100 x 100 m m and > 120 m m L/S of Wires : 10/10 m m ~1.3 mm 2015/07/08 ISEC 2015 NAGOYA

Present status of STJ detector System energy resolution for 400 eV X-ray : 6.3 eV FWHM Intrinsic energy resolution : 4.7 eV FWHM (Pulser : 4.2 eV FWHM) The best energy resolution for Nb/Al STJ 7 times higher energy resolution than that of SDD Soft X-ray spectrum Histogram of D E @400 eV values 300 300 for type-II STJs Pulser x 0.1 6.3 eV of STJ 48 eV of SDD 250 6.7+/-1.0 eV 400 eV X-ray 200 200 (82 pixels) Counts Counts 150 100 100 50 0 0 200 250 300 350 400 450 500 300 350 400 450 500 Energy(eV) Energy (eV) DR-P18 : Go Fuji 2015/07/22 LTD-16 2015 Grenoble

Practical example of Nb/Al STJs made at CRAVITY Superconducting fluorescence-yield X-ray absorption fine structure apparatus(SC-XAFS) Feature ： 1. FY-XAFS apparatus utilizing a 100-pixel Nb/Al STJ array for soft X-ray detection. 2. XAFS spectra of trace light elements in matrices can be obtained. 3. Information of atomic-scale local structures in advanced functional materials (semiconductor with low energy consumption, spintronics, solar cells, and magnetism) can be obtained. （ Competitor: Advanced Light Source in USA ） Specifications and appearances a Usage examples 3C Analysis of • Trace light elements in wide gap semiconductor • Na dopant in CIGS solar cells Si site • Mg dopant in LEDs. Absorption [a.u.] C site 4H FEFF Si sites C sites 380 400 420 440 460 Photon energy [eV] b • Energy resolution of X-rays ： 10 eV • Energy range of X-ray ： 100 eV - 15 keV (<2 keV: Nb/Al STJ array, > 2keV:SSD ） • Pixel number ： 100 • Maximum counting rate of X-rays ： 1 Mcps • Cooling : Automatic cryostat without a liquid helium （ operation temperature : 0.3 K ） Figure 2 Ab initio multiple scattering Figure 1. XANES spectra of n-type calculations. (a) XANES spectra dopant N atoms(300 ppm) in SiC M. Ohkubo et al ., Scientific Reports , 2 , 831 calculated with FEFF8.424 for the N in the as-implanted state and DOI: 10.1038/srep00831 (2012). atoms in 4H- and 3C-SiC. (b) Crystal after annealing at 1400 or ISEC 2015 NAGOYA 2015/07/08 structure models of the N-doped 1800 ℃ .

Application fields of SC detectors Materials analysis : dopant analysis for developing functional and structural materials. SR Physical chemistry a b 3C Electrostatic Storage Ring Si site Absorption [a.u.] C site 4H Si sites Space physics C sites 380 400 420 440 460 Photon energy [eV] Mass analysis of neutral molecule fragments with dissociative recombination (DR) Determination of neutrino mass LTD-16 2015 Grenoble 2015/07/22