Dissertation > Excellent graduate degree dissertation topics show

Research on Superconducting NbN, NbTi Films Preparation and Related Devices

Author: LiuXiaoYu
Tutor: KangLin
School: Nanjing University
Course: Radio Physics
Keywords: Magnetron sputtering technology superconducting NbN films superconducting NbTi film AlN films NbN HEB device
CLC: TN773
Type: Master's thesis
Year: 2011
Downloads: 51
Quote: 0
Read: Download Dissertation

Abstract


Superconducting hot electron mixer (HEB) has a unique advantage in the attractive 0.1～6THz band because of its low local power requirements and unlimited operating frequency to superconducting energy gap. Therefore, it has a wide range of applications in astronomy, atmospheric ozone detection, and detection of THz imaging. The main work in this thesis is to study the fabrication of superconducting NbN, NbTi thin film, and the design and preparation of the phonon cooled HEB mixers based on the superconducting thin films.The fabrication and Properties of NbN, NbTi Thin FilmsUsing Magnetron sputtering technology, we fabricated 4-8nm ultra-thin superconducting NbN films on single crystal Si substrates with different sputtering pressure and different mixing ratio of gases. For the 4nm thick NbN films, the superconducting transition temperature(Tc0) was 7.1K, superconducting critical current density reached the order of 106 A/cm2.In addition to Sputtering of the NbN films, we also fabricated the superconducting NbTi thin films of different thickness using a target ratio is 53:47(purity of 99.9%). Through continuous improvement, we prepared 6.5nm thick NbTi thin films, and its Tc0 reached 6.8K. Jc reached 106 A/cm2.We found that NbTi superconducting films will decline rapidly because of the oxygen affinity. To solve this problem, a layer of AlN insulating film was prepared on the surface of NbTi films to cut off contact with the air. Then the NbTi superconducting properties of thin films did not change over time, but also the Tc0 of the thin film of 6.5nm thick, covered with 1nm AlN of NbTi films,reached 7.1K.HEB device performance testAccording to the superconducting properties of NbN thin films, we designed NbN HEB device, and by electron beam lithography, reactive ion etching (RIE), lithography and other processes, we prepared NbN HEB devices. In the key process-the preparation of micro-bridge, before the electrode preparation, we improved the quality of NbN by adding the ionic cleaning process and got a micro-bridge with a clear edged 0.4×4μm2 micro-bridge structure. This ensured the performance of NbN HEB device.After successfully prepared NbN HEB devices, we measured the IV curves under DC voltage source. Using the noise-temperature measurement system in the lab, we measured noise temperature of NbN HEB devices. NbN HEB is highly sensitive to external high-frequency signals. At 1.6THz, noise temperature can reach 1668K.

Related Dissertations

  1. Vertical-cavity Surface-emitting Semiconductor Laser Insulation Membrane Technology Research,TN365
  2. Design and Performance Study for AlN as the Gate Dielectric Material Applied to Nano-scale MOS Devices,TN386.1
  3. Simulation Study of AlN Adsorption on the α-Al2O3（0001） Surface,O647.31
  4. Structure and Properties of AlN and Fe-doped AlN Films,TB383.2
  5. AIN films for FBAR technology,TN713
  6. Preparation of Carbon Nanomaterials and Their Application in Composite,TB383.1
  7. The Research and Design of Phase Conjugation Mixer in Retro-directive Array,TN773
  8. Study on NbN Hot Electron Bolometer Mixer,TN773
  9. Microwave frequency components and research,TN773
  10. Applied Research of AFE in High-voltage Inverter,TN773
  11. Research on Intelligent Fault Diagnosis and Its Application in Inverter,TN773
  12. The Research and Application of DSP and FPGA in High Voltage Frequency Conversion,TN773
  13. The Modeling and Simulation of a Regenerative Medium-Voltage Inverter Based on the Cascaded H-bridges,TN773
  14. Design of a Low-Power and High Linearity CMOS Down-Conversion Mixer,TN773
  15. CMOS image rejection mixer circuit design for digital TV tuner,TN773
  16. The Design and Realization of Digital Down Converter Based on FPGA,TN773
  17. Current Commutating Passive Sub-harmonic Mixer Design for Zero-IF Receiver,TN773
  18. Design of Digital Up-converter Based on FPGA,TN773
  19. Study on Frequency Division Control Strategy and Dynamic Transition Process of Six-pulse Cycloconverter,TN773
  20. Research on the DSP Based Controlled Method for Frequency-variable High Voltage Device,TN773
  21. Software Radio Digital Down Converter Technology Research and Implementation,TN773

CLC: > Industrial Technology > Radio electronics, telecommunications technology > Basic electronic circuits > Multiplier, divider,inverter > Inverter, mixer
© 2012 www.DissertationTopic.Net  Mobile