An integrated superconductive magnetic nanosensor for high-sensitivity nanoscale applications

Granata, C.; Esposito, E.; Vettoliere, A.; Petti, Lucia; Russo, M.

doi:10.1088/0957-4484/19/27/275501

Cited by 80 publications

(63 citation statements)

References 31 publications

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Section: Introductionmentioning

confidence: 99%

“…Above a few tens of Hz the low frequency 1/f -like noise changes into white noise on the level of 3 × 10 −5 to 1.8 × 10 −6 Φ 0 / √ Hz over a wide range of fields, which translates into a field sensitivity of 1.1 × 10 −7 T. Our flux sensitivity is comparable to that of state of the art SQUIDs, 21 yet the area of the SOT loop is only 0.034 µm 2 , which is the smallest reported to date. 4,9 The small size of SOT is highly advantageous for spin detection since spin sensitivity in units of µ B / √ Hz is given bywhere R is the radius of the loop, h is the height of the loop above the spin dipole, r e = 2.82 ×10 −15 m, and Φ n is the flux sensitivity in Φ 0 / √ Hz. 12,22 For h < R we obtain spin sensitivity of 65 We have integrated the SOT into a scanning probe microscope operating at 300 mK in which the tip is glued to one tine of a quartz tuning fork.…”

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confidence: 99%

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Self-Aligned Nanoscale SQUID on a Tip

et al. 2010

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A nanometer-size superconducting quantum interference device (nanoSQUID) is fabricated on the apex of a sharp quartz tip and integrated into a scanning SQUID microscope.A simple self-aligned fabrication method results in nanoSQUIDs with diameters down to 100 nm with no lithographic processing. An aluminum nanoSQUID with an effective area of 0.034 µm 2 displays flux sensitivity of 1.8 × 10 −6 Φ 0 / √ Hz and operates in fields as high as 0.6 T.With projected spin sensitivity of 65 µ B / √ Hz and high bandwidth, the SQUID on a tip is a highly promising probe for nanoscale magnetic imaging and spectroscopy.Imaging magnetic fields on a nanoscale is a major challenge in nanotechnology, physics, chemistry, and biology. One of the milestones in this endeavor will be the achievement of sensitivity sufficient for detection of the magnetic moment of a single electron. patterning methods; 3-11 the large in-plane size of the devices precludes bringing the SQUID loop into sufficiently close proximity to the sample (due to alignment issues) to scan it with optimal sensitivity. Recently, a terraced SQUID susceptometer was developed that is based on a multilayered lithographic process combined with FIB etching. This device includes a 600 nm pickup loop which can be scanned 300 nm above the sample surface. 12 Here we present a simple method for the self-aligned fabrication of a DC nanoSQUID on a tip with effective diameter as small as 100 nm that can be scanned just a few nm above the sample.We have fabricated several SQUID-on-tip (SOT) devices of various sizes. A quartz tube of 1 mm outside diameter is pulled to a sharp tip with apex diameter that can be controllably varied between 100 and 400 nm. The fabrication of the SOT consists of three "self-aligned" steps of thermal evaporation of Al, as shown schematically in Fig. 1a. In the first step, 25 nm of Al are deposited on the tip tilted at an angle of -100 • with respect to the line to the source. Then the tip is rotated to an angle of 100 • , followed by a second deposition of 25 nm. As a result, two leads on opposite sides of the quartz tube are formed, as shown in Fig. 1b. In the last step 17 nm of Al are evaporated at an angle of 0 • , coating the apex ring of the tip. The two areas where the leads contact the ring form "strong" superconducting regions, whereas the two parts of the ring in the gap between the leads, indicated by arrows in Fig. 1c, constitute two weak links, thus forming the SQUID. The resulting nanoSQUID requires no lithographic processing, its size is controlled by a conventional pulling procedure of a quartz tube, and it is located at the apex of a sharp tip that is ideal for scanning probe microscopy.The studies were carried out at 300 mK, well below the critical temperature T c ≈ 1.6 K of granular thin films of aluminum in our deposition system. Instead of the commonly used current 2 bias, the SOT was operated in a voltage bias mode, as shown schematically in the inset to Fig. 2. We use a low bias resistance R b of about 2 Ω and the SOT current...

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

Self-Aligned Nanoscale SQUID on a Tip

et al. 2010

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“…The superconducting loop has a washer shape in order to enhance the heat dissipation during the working operations when the sensor is current biased in resistive mode. The sample fabrication procedure has been described in details elsewhere [7], so only an outline of the sensor design and the main fabrication steps is given here. The fabrication process is based on thin films patterned by both electron beam lithography (EBL) and optical lithography as well as lift off and reactive ion etching (RIE) processes.…”

Section: Sample Fabrication and Sensor Performancementioning

confidence: 99%

“…Due to their insensitivity to background magnetic fields, such nano-SQUIDs are ideal for making local magnetic measurements. Reaching a spectral density of magnetic moment noise as low as few µ B /Hz 1/2 [5][6][7][8] (µ B is the Bohr magneton) referred to a sensor geometrical area of about (200 x 200 nm2), the nano-SQUIDs are suitable for the above cited applications. Recently, preliminary measurements of magnetization from ferritin nano-particles have been reported [6].…”

Section: Introductionmentioning

confidence: 99%

“…Dayem nano-bridges (nano-constriction of a superconducting film) fabricated by using Electron Beam Lithography (EBL) or Focused Ion Beam (FIB) represent a good alternative to the tunnel type junctions. So, a nano-SQUID consists typically of a niobium thin film ring (diameter of 100-400 nm) interrupted by two nano-bridges with a length and a width of less than one hundred of nanometers [5][6][7][8]. In the present paper, a detailed study of these devices is reported.…”

Section: Introductionmentioning

confidence: 99%

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NANO-SQUIDs based on niobium Dayem bridges for nanoscale applications

Granata

Vettoliere

Walke

et al. 2010

J. Phys.: Conf. Ser.

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Abstract. We report on the design, the fabrication and the performance of an integrated magnetic nano-sensor based on niobium dc-SQUID (Superconducting QUantum Interference Device) for nanoscale applications is presented. The nano-sensors are based on nanometric niobium constrictions (Dayem bridges) inserted in a square loop having a side length of 200 nm. Measurements of voltage-flux characteristic, flux to voltage transfer factor and noise performances are reported. In small signal mode, the sensors have shown a magnetic flux noise spectral density of 1.5 µΦ 0 /Hz 1/2 corresponding to a spin sensitivity in unit of Bohr magneton of 60 spin/Hz 1/2 . Supercurrent decay measurements of these devices are also reported. Such measurements provide useful information for applications which employ the SQUID as a trigger where the sensor works on the zero voltage state. The experimental data, have shown an intrinsic current fluctuation less than 0.2% of the critical current at liquid helium temperature, corresponding to an intrinsic sensor magnetic flux resolution of a few mΦ 0 . In view of the nano-SQUID employments in the detection of small spin populations, the authors calculated the spin sensitivity and the magnetic response relative to the single spin, as a function of its position within the SQUID hole. The results show that the SQUID response depends strongly on the spin position.

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Electrical and Electronic Composites

Valentino

2012

Wiley Encyclopedia of Composites

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An integrated superconductive magnetic nanosensor for high-sensitivity nanoscale applications

Cited by 80 publications

References 31 publications

Self-Aligned Nanoscale SQUID on a Tip

Self-Aligned Nanoscale SQUID on a Tip

NANO-SQUIDs based on niobium Dayem bridges for nanoscale applications

Electrical and Electronic Composites

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