pseudo-Hall Effect Research Articles

Transport through dynamic pseudogauge fields and snake states in a Corbino geometry

We propose a Corbino-disk geometry of a graphene membrane under out-of-plane strain deformations as a convenient path to detect pseudo-magnetic and electric fields via electronic transport. The three-fold symmetric pseudo-magnetic field changes sign six times as function of angle, leading to snake states connecting the inner and outer contacts and to nearly quantized transport. For dynamical strain obtained upon AC gating, the system supports an AC pseudo-electric field which, in the presence of the pseudo-magnetic field, produces a net electronic charge current in the absence of an external voltage, via a pseudo-Hall effect.

A large pseudo-Hall effect in n-type 3C-SiC(1 0 0) and its dependence on crystallographic orientation for stress sensing applications

The pseudo-Hall effect in n-type single crystal 3C-SiC(100) with low carrier concentration has been investigated. Low pressure chemical vapor deposition was used to grow the single crystal n-type 3C-SiC(100) and Hall devices were fabricated by photolithography and dry etch processes. A large pseudo-Hall effect was observed in the grown thin films which showed a strong dependence on the crystallographic orientation. N-type 3C-SiC(100) with low carrier concentration shows a completely different behavior of pseudo-Hall measurements as compared to the p-type 3C-SiC(100). Contrary to p-type, the effect is maximum along [100] crystallographic orientation and minimum along [110] orientation. Moreover, the observed pseudo-Hall effect is 50% larger than p-type with higher carrier concentration grown by the same process which makes n-type 3C-SiC(100) with low carrier concentration more suitable material for designing highly sensitive micro-mechanical sensors.

Pseudo-Hall Effect in Graphite on Paper Based Four Terminal Devices for Stress Sensing Applications

A cost effective and easy to fabricate stress sensor based on pseudo-Hall effect in Graphite on Paper (GOP) has been presented in this article. The four terminal devices were developed by pencil drawing with hand on to the paper substrate. The stress was applied to the paper containing four terminal devices with the input current applied at two terminals and the offset voltage observed at other two terminals called pseudo-Hall effect. The GOP stress sensor showed significant response to the applied stress which was smooth and linear. These results showed that the pseudo-Hall effect in GOP based four terminal devices can be used for cost effective, flexible and easy to make stress, strain or force sensors.

Pseudo-Hall Effect in Single Crystal n-Type 3C-SiC(100) Thin Film

This article reports the first results on stress induced pseudo-Hall effect in single crystal n-type 3C-SiC(100) grown by LPCVD process. After the growth process, Hall devices were fabricated by standard photolithography and dry etching processes. The bending beam method was employed to study the stress induced changes in the electrical response of the fabricated Hall devices. It has been observed that when stress is applied to the 3C-SiC(100) Hall devices, the offset voltage of the Hall devices varies linearly with the applied compressive and tensile stresses which is called, the pseudo-Hall effect. The variation of the offset voltage of these Hall devices is also proportional to the applied input current. This variation of the offset voltage with the applied compressive and tensile stresses shows that single crystal n-type 3C-SiC(100) can be used for stress sensing applications.

Pseudo-Hall effect in single crystal 3C-SiC(111) four-terminal devices

This article reports the first results on the strain-induced pseudo-Hall effect in single crystal 3C-SiC(111) four-terminal devices.

Orientation dependence of the pseudo-Hall effect in p-type 3C–SiC four-terminal devices under mechanical stress

This study reports on the orientation dependence and shear piezoresistive coefficients of the pseudo-Hall effect in p-type single crystalline 3C–SiC.

Electronic transport properties of a tilted graphenep−njunction

Spatial manipulation of current flow in graphene could be achieved through the use of a tilted $p\text{\ensuremath{-}}n$ junction. We show through numerical simulation that a pseudo-Hall effect (i.e., nonequilibrium charge and current density accumulating along one of the sides of a graphene ribbon) can be observed under these conditions. The tilt angle and the $p\text{\ensuremath{-}}n$ transition length are two key parameters in tuning the strength of this effect. This phenomenon can be explained using classical trajectory via ray analysis, and is therefore relatively robust against disorder. Lastly, we propose and simulate a three terminal device that allows direct experimental access to the proposed effect.

Simultaneous and Independent Measurement of Stress and Temperature Using a Single Field-Effect Transistor Structure

This paper reports on the simultaneous and independent measurement of mechanical stress and temperature using p- and n-channel field-effect transistor structures with multiple drain/source contacts fabricated in a commercial complementary metal-oxide-semiconductor technology. The respective average stress sensitivities of of three p-channel devices and 66 of two n-channel devices at room temperature originate from the shear piezoresistance effect, also termed pseudo-Hall effect, of the inversion layer carriers. The stress sensitivities show very small average temperature coefficients (TCs) of 1127 and 431 ppm/K for the p- and n-channel devices, respectively. Temperature values were obtained from the temperature-dependent threshold voltage . Robust values were extracted from the second-order transconductance smoothed using a new variant of Tikhonov's regularization method. With both types of devices, the obtained by this procedure was found to be stress insensitive in the range of stresses from 0 to 20.4 MPa. Between 25 and 150 , depends linearly on temperature, with average slopes of 1.67 and for p- and n-channel devices, respectively. Device-to-device variations of the temperature sensitivity and its slope suggest the use of a two-point calibration. With only a one-point calibration, a temperature uncertainty of less than 3 over a temperature range of 100 is achieved.

Piezo-FET Stress-Sensor Arrays for Wire-Bonding Characterization

This paper reports the design, fabrication, and characterization of a two-dimensional stress-sensor array based on a stress-sensor element exploiting the transverse pseudo-Hall effect in metal-oxide-semiconductor (MOS) field effect transistors (FET). P-channel MOS (PMOS) devices were integrated in a 4/spl times/4 stress sensor array with a total area of 120/spl times/120 /spl mu/m/sup 2/. The individual elements of the array are sensitive to the local shear stress in the chip plane. They are selected using a CMOS integrated digital decoder and transmission gates. The new array was characterized using a commercial ball-wedge wire bonding tool and was used for the in situ monitoring of the bonding process. The spatially resolved measurement of the stress distribution underneath and close to a bond pad during the bond wire touch-down is demonstrated. The array is able to resolve variations in the touch-down position of 10 /spl mu/m. The time of 1.6 ms for acquisition of a full frame is currently limited by the experimental setup. To monitor the stress distribution during the bonding process, an aluminum covered stress sensor array similar to a standard bond pad was used. The successful bond formation between a gold ball and the metal bond pad was observed. The bond formation becomes evident as a characteristic, concentrated stress profile with large peak value appearing within 20 ms. The maximum stresses underneath the successfully bonded area exceeds stress levels in unbonded sensor locations by a factor of up to 60.

Geometry optimization for planar piezoresistive stress sensors based on the pseudo-Hall effect

The dependence of the sensitivity of planar piezoresistive stress sensors on geometry is systematically analyzed. The sensors in this paper are based on the shear piezoresistance effect, also termed pseudo-Hall effect. The analyzed geometry parameters are: (i) the shape of the device active area, (ii) its aspect ratio and (iii) the location and size of input and output contacts. Further, the influence of non-conducting islands in the active device area was investigated. General design rules for the design of piezoresistive stress sensors with improved sensitivity were extracted. These results were obtained using a simulation approach combining affine mapping with the finite element method. The simulation program was tested by comparing simulation results with experimental data obtained from stress sensors fabricated in CMOS technology. The differences between simulated and measured results were between 1.2 and 3.3%. Novel optimized sensor geometries with non-conducting islands show simulated and measured sensitivities greatly improved by factors up to 2.30 and 2.39, respectively. Further, the new sensors with non-conducting islands are put in perspective with classical Wheatstone bridges.

Ferromagnetic domain structure and hysteresis of exchange bias in NiFe/NiMn bilayers

Magnetization reversal in NiFe/NiMn bilayers was studied by measuring anisotropic magnetoresistance and pseudo-Hall effect simultaneously. Since the single domain state of the ferromagnetic layer could be well traced in such measurements, we were able to distinguish hysteresis of exchange bias from inhomogeneous magnetization. The exchange bias was found to have two components during the single domain reversal process. Domain breaking in given fields took place when the biasing field became more random.

Narrow-range angle sensor based on wiggles in angular dependence of pseudo-Hall effect

In this paper, for the first time a new type of narrow-range angle sensor based on pseudo-Hall effect is introduced and studied. This sensor is designed to be sensitive to very small changes in angle with detected range is scaled down to about 0.5°. An intensive investigation has been carried out to study the behaviors of the sensor and optimize its performance. These behaviors are discussed and explained using an analytical simulation. Several designs for making the sensor on a Si wafer are suggested. Moreover, some applications of the sensor are proposed and a demo device based on the sensor is presented.

Exchange coupling in NiFe/NiMn films studied by pseudo-Hall effect

Pseudo-Hall effect in exchange biased NiFe/NiMn films was measured in magnetic fields rotated in the film plane. Besides accurate determination of the exchange biasing direction, coherent rotation and incoherent reversal of the magnetization of the NiFe layers can be distinguished from these measurements. Detailed magnetic anisotropy analysis shows that there is no additional uniaxial anisotropy induced by the interfacial coupling in this system, while the instability of antiferromagnetic grains may play an important role that is responsible for the difference between exchange biasing fields obtained by reversible and irreversible measurements.

Pseudo-Hall effect in spin-valve multilayers

Magnetoresistance and the pseudo-Hall effect in NiFe/Cu/NiFe/FeMn spin-valve multilayers were measured simultaneously in fields rotating in the film plane. Large pseudo-Hall voltages have been observed when the magnetization of the free layer was perpendicular to the sensing current, which was applied along the magnetization of the pinned layer. The pseudo-Hall voltages cannot be explained by treating the anisotropic magnetoresistance of the two permalloy layers independently. Such a cross effect of the free and pinned layers on the anisotropic magnetoresistance is dependent upon the angle between their magnetization.

Pseudo-Hall effect and anisotropic magnetoresistance in a micron-scale Ni/sub 80/Fe/sub 20/ device

The pseudo-Hall effect (PHE) and anisotropic magnetoresistance (AMR) in a micron-scale Ni/sub 80/Fe/sub 20/ six-terminal device, fabricated by optical lithography and wet chemical etching from a high quality UHV grown 30 /spl Aring/ Au/300 A Ni/sub 80/Fe/sub 20/ film, have been studied. The magnetisation reversal in different parts of the device has been measured using magneto-optical Kerr effect (MOKE). The device gives a 50% change in PHE voltage with an ultrahigh sensitivity of 7.3%Oe/sup -1/ at room temperature. The correlation between the magnetisation, magneto-transport properties, lateral shape of the device and directions of the external applied field is discussed based on extensive MOKE, AMR and PHE results.

Effects of sample size and field orientation on pseudo-Hall voltage in micronscale nickel thin-film squares

Pseudo-Hall effect (PHE) in Ni thin-film squares of 1–5 μm size is measured with a constant current through two leads along one diagonal of the square and the voltage output from leads along the other diagonal. The PHE voltage in response to an in-plane magnetic field depends on the square size and field orientation. The minimum PHE voltage at low field is close to zero only with the 2 μm square containing four symmetrical closure domains leading to a 600% relative change in PHE voltage. The PHE signal is found the largest when the field direction is along the square side while the smallest when along the square diagonal.