InAs quantum well Hall devices for room-temperature detection of single magnetic biomolecular labels

Abstract

Articles you may be interested inDetection of magnetically labeled DNA using pseudomorphic AlGaAs ∕ InGaAs ∕ GaAs heterostructure micro-Hall biosensors J. Appl. Phys. 99, 08P103 (2006); 10.1063/1.2162041Room-temperature electric-field controlled spin dynamics in (110) InAs quantum wells Hall sensors with cross width of ϳ1 m were fabricated from InAs/ AlSb quantum well semiconductor heterostructures containing two-dimensional electron gas. The room-temperature device characteristics were examined by Hall effect and electronic noise measurements along with analytical calculations. In the low-frequency range, from 20 Hz to 1.6 kHz, the noise-equivalent magnetic field resolution was found to be limited by 1 / f and generation-recombination noise from 22 to 3.5 T/ ͱ Hz. The corresponding noise-equivalent magnetic moment resolution reached 10 6 B / ͱ Hz at ϳ700 Hz and was even lower at higher frequencies. Using a phase-sensitive measurement technique, detection of a single 1.2 m diameter bead, suitable for biological applications, was achieved with a signal to noise ratio of ϳ33.3 dB, as well as detection of six 250 nm beads with a signal to noise of ϳ2.3 dB per bead. The work demonstrates the efficacy of InAs quantum well Hall devices for application in high sensitivity detection of single magnetic biomolecular labels.

Dynamic micro-Hall detection of superparamagnetic beads in a microfluidic channel

“…As the beads pass by the cross they alter the total average magnetic field over its sensing area and hence V H associated with it. Due to dipolar character [8,24] of the stray magnetic field, the total field penetrating each cross will either increase or decrease depending on the relative position of the beads with respect to the cross. Figure 2 shows a real-time V H signal recorded for one cross (the first one from the left in Figure 2(b)).…”

“…One bead partially covers one cross while the rest of the beads are in the vicinity of the other crosses. A Hall detection measurement as described by Mihajlović et al [9,24] was then performed. Here, the main difference from the dynamic measurement is that an additional dc magnetic field ( B = 70.6mT) was applied in order to reduce the induced ac magnetization of the beads.…”

“…by using Δ V H ∝ Δ B . Since the stray magnetic field from a SPM bead is dipolar [8,24] and since the Hall sensor is only sensitive to the perpendicular component, we can explicitly write this change in average field as $$\mathrm{\Delta }{B}_i=\frac{{\mu }_0\mathrm{\Delta }MV}{4\pi }{\displaystyle \sum _j{\displaystyle \underset{A_i}{\int }true\int \frac{\mathit{2}{z}^{\mathrm{italic2}}-{\mathit{(}x-x_j\mathit{)}}^{\mathrm{italic2}}-{\mathit{(}y-y_j\mathit{)}}^2}{{\mathit{(}{z}^{\mathrm{italic2}}+{\mathit{(}x-x_j\mathit{)}}^{\mathrm{italic2}}+{\mathit{(}y-y_j\mathit{)}}^{\mathrm{italic2}}\mathit{)}}^{\frac{\mathrm{italic5}}{\mathrm{italic2}}}}dxdy}}$$ where indices i and j correspond to the Hall cross and the beads respectively, Δ M is the change in magnetization of the bead due to the application of the dc field, V is the bead volume and A is the sensing area of the Hall cross over which the integration is performed. Since these beads are very uniform and to keep the calculations simple, we will assume that all beads have the same volume and the same change in magnetization and therefore we will be interested in the relative magnetic field change for each cross rather than the absolute values.…”

“…Micro-Hall devices have linear output and are not limited in the magnitude of the external magnetic fields that can be applied to magnetize SPM beads, which is advantageous for biodetection and necessary in magnetic separation. In particular, devices based on InAs quantum well (QW) semiconductor heterostructures have been recently demonstrated with a superb signal-to-noise (S/N) ratio in detection experiments performed with micrometer and nanometer sized beads [10,23,24]. Furthermore, since these devices are sensitive to the perpendicular component of the stray magnetic field generated by the beads, they can map out the trajectory of the moving beads.…”

Micro-Hall position sensing of magnetic nanowires

“…For example, a micro-Hall device of identical size, fabricated from InAs/ AlSb quantum well heterostructure containing 2DEG, exhibits room temperature N B min ϳ 5 T / ͱ Hz at 1 kHz. 17 From the results presented in Secs. III A and III B, it is clear that N x min will also depend on 0 M, R, and d. One should therefore evaluate N x min for each particular case, based on the equations presented in Sec.…”