Iron is an essential yet toxic redox active element that is found in many cells, including neurons and glial cells. Several techniques have been used to quantify iron in neurons and cells; however, most are incapable of high-resolution imaging inside a single cell. Magnetic field sensors based on diamond nitrogen vacancy (NV) centers have emerged as a powerful tool for detecting magnetic signal in iron-containing biological samples with a good combination of spatial resolution and sensitivity. In this study we use NV based T1 relaxometry technique to map iron in cytochrome C (Cyt C) proteins. Cyt C plays an important role in the electron transport chain of mitochondria and it is in the Fe(III) paramagnetic state under ambient conditions. We measure Cyt C under different concentrations and locations of the 10-nm NV doped diamond chip. We show a reduction of the NV T1 from few milliseconds to hundreds of microseconds, explained by the spin noise from the intracellular iron spins in the Cyt C protein. Additionally, we perform imaging of Cyt C proteins on a nanostructured diamond chip.
KEYWORDS: Magnetism, Magnetic sensors, Sensors, Annealing, Ruthenium, Temperature metrology, Microsoft Foundation Class Library, Nanostructures, Crystals, Tantalum
The development of high-sensitivity magnetic field sensors at low frequencies and ambient temperatures is of great importance for many practical applications, where different aspects of the sensor performance need to be considered. In this paper, it is presented that by tuning magnetic nanostructures of the free layers in magnetic tunnel junctions, widedynamic-range or ultra-high-sensitivity tunneling magnetoresistive sensors can be obtained. Tunneling magnetoresistive sensors with a linear response from -75 mT to +75 mT are demonstrated. Also, it is demonstrated that an optimized ultra-high-sensitivity magnetic sensor with a sensitivity of 57,790 %/mT can be achieved. This sensitivity is currently the highest among all magnetoresistive sensors that have been reported. The estimated noise of our magnetic sensor is 2.3 pT/Hz1/2 at 1 Hz and 190 fT/Hz1/2 at 100 Hz respectively. This tunneling magnetoresistive sensor dissipates only 25 μW of power when it operates under an applied voltage of 1 V at room temperature.
The methods for the optimization of the magnetoresistive (MR) sensors are to reduce sources of noises, to increase the signal, and to understand the involved fundamental limitations. The high-performance MR sensors result from important magnetic tunnel junction (MTJ) properties, such as tunneling magnetoresistance ratio (TMR), coercivity (Hc), exchange coupling field (He), domain structures, and noise properties as well as the external magnetic flux concentrators. All these parameters are sensitively controlled by the magnetic nanostructures, which can be tuned by varying junction free layer nanostructures, geometry, and magnetic annealing process etc. In this paper, we discuss some of efforts that an optimized magnetic sensor with a sensitivity as high as 5,146 %/mT. This sensitivity is currently the highest among all MR-type sensors that have been reported. The estimated noise of our magnetoresistive sensor is 47 pT/Hz1/2 at 1 Hz. This magnetoresistance sensor dissipates only 100 μW of power while operating under an applied voltage of 1 V at room temperature.
KEYWORDS: Single walled carbon nanotubes, Electrodes, Chemical vapor deposition, Molybdenum, Gas lasers, Carbon monoxide, Transistors, Field effect transistors, Semiconductors, Chemical lasers
Recent prominent progresses in synthesizing and manipulating single-walled carbon nanotubes (SWNTs) stimulated
extensive interests in developing SWNT-based devices for nanoelectronics and nanoelectromechanical systems (NEMS).
Thermal chemical vapor deposition (CVD) is one of the most widely accepted technique for growing SWNTs by heating
the whole chamber and substrate to required reaction temperatures. In this study, we demonstrated a process for position-controllable
synthesis of SWNT-FET by bridging the SWNT across pre-defined electrodes using the laser chemical
vapor deposition (LCVD) technique. The SWNT-FET was back-gate modulated, showing p-type semiconducting
characteristics. The process is very fast and can be conducted using both far-infrared CO2 laser (10.6 &mgr;m) and near-infrared
Nd:YAG laser (1064 nm). We have also demonstrated localized synthesis of SWNTs by a focused laser beam.
Due to the unique advantages of LCVD process, such as fast and local heating, as well as its potential to select chiralities
during the growing process, it may provide new features and versatilities in the device fabrication.
A detailed understanding of noise characteristics is essential for the design of a high signal-to-noise ratio (SNR) reader sensor. We intend to correlate the microstructure to the source of magnetic noises for improving the magnetic stability of the recording heads. A dynamic magnetic sensitivity mapping (MSM) system is designed to image the magnetic noise sources in sub-micrometer sized recording heads. A nanometer sized magnetic force microscopy (MFM) tip was used to apply a well-defined, localized magnetic field on the air bearing surface (ABS) of the head. For a certain area position of the free layer with incoherent rotation of the magnetic moment, this localized magnetic field will cause magnetic instability in the head, and this instability will show up as electrical noise on the output signal. Because most of the noise related to magnetic domain fluctuation is dominated at the low frequency region, our study concentrates on the spatial characterization of the noise source in a frequency range of 20 kHz to 60 kHz. Recording the average amplitude of the noise spectrum due to the excitation in the measured frequency range as a function of the tip's position, the location of the magnetic noise source can be identified. Magnetic noise images have been obtained by our system for some recording giant magnetoresistance (GMR) and tunnel magnetoresistance (TMR) recording heads. Noise MSM images of some unstable recording heads clearly show the spatially uneven noise.
Pulsed laser deposition is a technique commonly used to deposit high quality thin films of high temperature superconductors. This paper discusses the results obtained when this technique is applied to the deposition of Tl-Ca-Ba-Cu-O thin films using a frequency doubled Nd:YAG laser operating at 532 nm and an excimer laser operating at 248 nm. Films with onset temperatures of 125 K and zero resistance temperatures of 110 K deposited on (100) oriented MgO from a composite Tl2Ca2Ba2Cu3Ox target were obtained at both wavelengths upon appropriate post deposition annealing. Films deposited at 532 nm exhibit a rough surface, while those deposited at 248 nm are smooth and homogeneous. Upon annealing, films deposited at both wavelengths are single phase Tl2Ca2Ba2Cu3Ox.
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