Variable Temperature-Scanning Hall Probe Microscopy (VT-SHPM) with GaN/AlGaN Two-Dimensional Electron Gas (2DEG) Micro Hall Sensors in 4.2-425K range, Using Novel Quartz Tuning Fork AFM Feedback

In this report, we present the fabrication and variable temperature (VT) operation of Hall sensors, based on GaN/AlGaN heterostructure with a two-dimensional electron gas (2DEG) as an active layer, integrated with Quartz Tuning Fork (QTF) in atomic force-guided (AFM) scanning Hall probe microscopy (SHPM). Physical strength and wide band gap of GaN/AlGaN heterostructure makes it a better choice to be used for SHPM at elevated temperatures, compared to other compound semiconductors (AlGaAs/GaAs and InSb), which are unstable due to their narrower band gap and physical degradation at high temperatures. GaN/AlGaN micro Hall probes were produced using optical lithography and reactive ion etching. The active area, Hall coefficient, carrier concentration and series resistance of the Hall sensors were ~14m x 14m, 10m7/G at 4.2K, 6.3 x 1012cm-2 and 12k7 at room temperature and 7m7/G, 8.9 x 1012cm-2 and 24k7 at 400K, respectively. A novel method of AFM feedback using QTF has been adopted. This method provides an advantage over STM feedback, which limits the operation of SHPM the conductive samples and failure of feedback due to high leakage currents at high temperatures. Simultaneous scans of magnetic and topographic data at various pressures (from atmospheric pressure to high vacuum) from 4.2K to 425K will be presented for different samples to illustrate the capability of GaN/AlGaN Hall sensors in VT-SHP

Magnetic sensitive scanning probe microscopy

Magnetically sensitive scanning probe microscopes have been solving scientific and engineering problems over the last two decades. The magnetic dipole fields generated by a spherical magnetic particle with radius a decay with math. As the magnetic features of interest become smaller and smaller, the sensitivity of the apparatus has to be improved dramatically in order to measure and image the magnetic features within the specimen. An overview of these powerful methods is given in this article

Imaging Capability of PHEMT, GaN/AlGaN and Si Micro Hall Probes for Scanning Hall Probe Microscopy between 25°C-125°C

R. Akram, M. Dede and A. Ora

Imaging capability of pseudomorphic high electron mobility transistors, AlGaN/GaN, and Si micro-Hall probes for scanning Hall probe microscopy between 25 and 125°C

The authors present a comparative study on imaging capabilities of three different micro-Hall probe sensors fabricated from narrow and wide band gap semiconductors for scanning hall probe microscopy at variable temperatures. A novel method of quartz tuning fork atomic force microscopy feedback has been used which provides extremely simple operation in atmospheric pressures, high-vacuum, and variable-temperature environments and enables very high magnetic and reasonable topographic resolution to be achieved simultaneously. Micro-Hall probes were produced using optical lithography and reactive ion etching process. The active area of all different types of Hall probes were 1×1 µm2. Electrical and magnetic characteristics show Hall coefficient, carrier concentration, and series resistance of the hall sensors to be 10 mOmega/G, 6.3×1012 cm−2, and 12 kOmega at 25 °C and 7 mOmega/G, 8.9×1012 cm−2 and 24 kOmega at 125 °C for AlGaN/GaN two-dimensional electron gas (2DEG), 0.281 mOmega/G, 2.2×1014 cm−2, and 139 kOmega at 25 °C and 0.418 mOmega/G, 1.5×1014 cm−2 and 155 kOmega at 100 °C for Si and 5–10 mOmega/G, 6.25×1012 cm−2, and 12 kOmega at 25 °C for pseudomorphic high electron mobility transistors (PHEMT) 2DEG Hall probe. Scan of magnetic field and topography of hard disc sample at variable temperatures using all three kinds of probes are presented. The best low noise image was achieved at temperatures of 25, 100, and 125 °C for PHEMT, Si, and AlGaN/GaN Hall probes, respectively. This upper limit on the working temperature can be associated with their band gaps and noise associated with thermal activation of carriers at high temperatures

Variable temperature-scanning hall probe microscopy with GaN/AlGaN two-dimensional electron gas (2DEG) micro hall sensors in 4.2-425K range using novel quartz tuning fork AFM feedback

In this report, we present the fabrication and variable temperature (VT) operation of Hall sensors, based on GaN/AlGaN heterostructure with a two-dimensional electron gas (2DEG) as an active layer, integrated with Quartz Tuning Fork (QTF) in atomic force-guided (AFM) scanning Hall probe microscopy (SHPM). Physical strength and wide band gap of GaN/AlGaN heterostructure makes it a better choice to be used for SHPM at elevated temperatures, compared to other compound semiconductors (AlGaAs/GaAs and InSb), which are unstable due to their narrower band gap and physical degradation at high temperatures. GaN/AlGaN micro Hall probes were produced using optical lithography and reactive ion etching. The active area, Hall coefficient, carrier concentration and series resistance of the Hall sensors were ~14m x 14m, 10m7/G at 4.2K, 6.3 x 10^12cm-2 and 12k7 at room temperature and 7m7/G, 8.9 x 10^12cm-2 and 24k7 at 400K, respectively. A novel method of AFM feedback using QTF has been adopted. This method provides an advantage over STM feedback, which limits the operation of SHPM the conductive samples and failure of feedback due to high leakage currents at high temperatures. Simultaneous scans of magnetic and topographic data at various pressures (from atmospheric pressure to high vacuum) from 4.2K to 425K will be presented for different samples to illustrate the capability of GaN/AlGaN Hall sensors in VT-SHP

Non-Contact Lateral Force Gradient Measurement with Small Amplitude Off-Resonance Atomic Force Microscopy

M. Atabak, Ö. Ünverdi, H.Ö. Özer & A. Ora

Design of a self-aligned, wide temperature range (300 mK-300 K) atomic force microscope/magnetic force microscope with 10 nm magnetic force microscope resolution

We describe the design of a wide temperature range (300 mK-300 K) atomic force microscope/magnetic force microscope with a self-aligned fibre-cantilever mechanism. An alignment chip with alignment groves and a special mechanical design are used to eliminate tedious and time consuming fibre-cantilever alignment procedure for the entire temperature range. A low noise, Michelson fibre interferometer was integrated into the system for measuring deflection of the cantilever. The spectral noise density of the system was measured to be similar to 12 fm/root Hz at 4.2 K at 3 mW incident optical power. Abrikosov vortices in BSCCO(2212) single crystal sample and a high density hard disk sample were imaged at 10 nm resolution to demonstrate the performance of the system. (C) 2014 AIP Publishing LLC

Some production traits of indigenous Hair goats bred under extensive conditions in Turkey. 1st communication: reproduction, milk yield and hair production traits of does

This study was conducted to investigate the reproductive performance, milk yield, hair production, fleece characteristics and body weight after shearing of Hair goats (Anatolian Black Goats), bred under extensive conditions in Turkey. The material of the study was formed a total data of 456 Flair goats, which were between 2 and 7 years of age bred in the period of two years. Conception rate, infertility Fate, abortion rate, kidding rate, single birth Fate, twin birth rate, the percentage of kids born according to mated does and litter size were 97.81%, 2.19%. 3.59%, 94.30%. 97.91%., 2.09%, 96.27% and 1.02, respectively. Lactation length, milk yield in lactation period milking period and milk yield in milking period of goats were determined as 232.29 days, 100.92 kg, 132,09 days and 43.14 kg, respectively. Hair production, fibre diameter and staple length of Hair goats in the study were determined as 381.00 g, 76.70 micrones and 13.63 cm, respectively. It was found that the effects of production year and farm on the reproductive traits given by percentage weren't statistically significant. whereas the difference among production years for litter size was significant. It was found that the effect of production year oil milk production traits except for lactation length and on the hair production; the effect of farm factor on the hair production, staple length and live weigth after shearing, the effect of age on the milk production traits, hair production traits and live weight after shearing the effect of live weight on the hair production were statistically significant (p<0.05)

Construction of a scanning tunneling microscope and first results

Ankara : The Department of Physics and the Institute of Engineering and Sciences of Bilkent Univ. , 1990.Thesis (Master's) -- Bilkent University , 1990.Includes bibliographical references leaves 68-77.In this thesis, construction of a Scanning Tunneling Microscope in air is explained. A step motor sample approach mechanism and a tripod scanner are used in the construction. Atomic resolution images of graphite samples are obtained in both constant current and constant height modes. Loss of trigonal symmetry in some Graphite images are also observed. This anomaly is attributed to the multiple atom tip or slipped top layer of Graphite.Oral, AhmetM.S