Subjects: Engineering and technical science >> Physics Related Engineering and Technology Subjects: Engineering and technical science >> Technology of Instrument and Meter Subjects: Electronics and Communication Technology >> Electron Technology Subjects: Physics >> Interdisciplinary Physics and Related Areas of Science and Technology submitted time 2024-05-06
Abstract: In this work, a design of transimpedance amplifier (TIA) for cryogenic scanning tunneling microscope (CryoSTM) is proposed. The TIA with the tip-sample component in CryoSTM is called as CryoSTM-TIA. With transimpedance gain of 1 Gohm, the bandwidth of the CryoSTM-TIA is larger than 200 kHz. The distinctive feature of the proposed CryoSTM-TIA is that its pre-amplifier is made of a single cryogenic high electron mobility transistor (HEMT), so the apparatus equivalent input noise current power spectral density at 100 kHz is lower than 6 (fA)2/Hz. In addition, bias-cooling method can be used to in-situ control the density of the frozen DX- centers in the HEMT doping area, changing its structure to reduce the device noises. With this apparatus, fast scanning tunneling spectra measurements with high-energy-resolution are capable to be performed. And, it is capable to measure scanning tunneling shot noise spectra (STSNS) at the atomic scale for various quantum systems, even if the shot noise is very low. It provides a powerful tool to investigate novel quantum states by measuring STSNS, such as detecting the existence of Majorana bound states in the topological quantum systems.
Peer Review Status:Awaiting Review
Subjects: Electronics and Communication Technology >> Electron Technology Subjects: Engineering and technical science >> Physics Related Engineering and Technology Subjects: Physics >> Interdisciplinary Physics and Related Areas of Science and Technology Subjects: Engineering and technical science >> Technology of Instrument and Meter submitted time 2023-05-01
Abstract: In this work, a design of large-bandwidth high-gain low-noise transimpedance amplifier (TIA) for scanning tunneling microscope (STM) is proposed. The simulations show that the proposed TIA has the bandwidth higher than 200 kHz, two orders of magnitude higher than those of conventional commercial TIAs for STM. At low frequencies, the noises of the proposed TIA are almost the same as the conventional commercial ones with the same transimpedance gain. At high frequencies, its calculated input equivalent noise voltage power spectral density (PSD) is 40 (nV)2/Hz and its input equivalent noise current PSD is 3.2 (fA)2/Hz at 10 kHz. The corresponding values are 23 (nV)2/Hz and 88 (fA)2/Hz at 100 kHz. The STM with the proposed TIA can meet the needs of fast high-quality STM imaging measurements and fast high-energy-resolution scanning tunneling spectra measurements for the low-conducting materials, such as complex organic systems and wide bandgap semiconductors.
Subjects: Engineering and technical science >> Physics Related Engineering and Technology Subjects: Engineering and technical science >> Technology of Instrument and Meter Subjects: Electronics and Communication Technology >> Electron Technology Subjects: Physics >> Interdisciplinary Physics and Related Areas of Science and Technology submitted time 2023-05-01
Abstract: An ultra-low-noise large-bandwidth transimpedance amplifier (TIA) for cryogenic scanning tunneling microscope (CryoSTM) is proposed. The TIA connected with the tip-sample component in CryoSTM is called as CryoSTM-TIA. Its transimpedance gain is as high as 1 GΩ, and its bandwidth is over 300 kHz, but its equivalent input noise current power spectral density is less than 4 (fA)2/Hz at 100 kHz. The low inherent noise for the CryoSTM-TIA is due to its special design: (1) its pre-amplifier is made of a pair of low-noise cryogenic high electron mobility transistors (HEMTs); (2) the noise generated by one HEMT is eliminated by a large capacitor; (3) the capacitance of the cable connected the gate of the other HEMT to the tip is minimized; (4) thermal noise sources, such as the feedback resistor, are placed in the cryogenic zone. The dc output voltage drift of the CryoSTM-TIA is very low, as 5 μV/°C. The apparatus can be used for measuring the scanning tunneling differential conductance spectra, especially the scanning tunneling shot noise spectra (STSNS) of quantum systems, even if the shot noise is very low. It provides a universal tool to study various novel quantum states by measuring STSNS, such as detecting the Majorana bound states.
Subjects: Engineering and technical science >> Physics Related Engineering and Technology Subjects: Engineering and technical science >> Technology of Instrument and Meter Subjects: Electronics and Communication Technology >> Electron Technology Subjects: Physics >> Interdisciplinary Physics and Related Areas of Science and Technology submitted time 2022-12-29
Abstract:
A low-noise high-gain large-bandwidth transimpedance amplifier (TIA) for cryogenic scanning tunneling microscope (CryoSTM) is proposed. The TIA connected with the tip-sample component in CryoSTM is called as CryoSTM-TIA. The CryoSTM-TIA has a transimpedance gain of 10 Gohm, a bandwidth of over 100 kHz, and an equivalent input noise current power spectral density less than 4 (fA)2/Hz at 100 kHz. The low inherent noise of the CryoSTM-TIA is due to its special design: (1) its pre-amplifier (Pre-Amp) is made of the low-noise cryogenic high electron mobility transistors; (2) the cascode-type configuration for the Pre-Amp is used to avoid Miller effect to reduce its input capacitance CA; (3) the capacitance of the cable connected the Pre-Amp input to the tip, i.e. CI, is minimized; (4) thermal noise sources, such as the feedback resistor, are placed in the cryogenic zone. Its high gain and large-bandwidth are realized together, due to the application of the frequency compensation in the feedback loop, the reduced CA, and the minimized CI. This apparatus can be used for fast high-energy-resolution measurements of scanning tunneling spectra for low conductivity materials, especially for measuring their scanning tunneling shot noise spectra.
Subjects: Engineering and technical science >> Physics Related Engineering and Technology Subjects: Engineering and technical science >> Technology of Instrument and Meter Subjects: Electronics and Communication Technology >> Electron Technology Subjects: Physics >> Interdisciplinary Physics and Related Areas of Science and Technology submitted time 2022-12-29
Abstract: Shot noise is a powerful tool to study quantum systems. In this work, a design of transimpedance amplifier (TIA) for a cryogenic scanning tunneling microscope (CryoSTM) is proposed to meet the requirements of the shot noise measurements for quantum systems. In the TIA, the preamplfier is made of the low-noise low-power cryogenic high electron mobility transistors. With the high transimpedance gain of 1 Gohm, the bandwidth of the proposed TIA is larger than 300 kHz. In the CryoSTM, the TIA with the tip-sample component is called as CryoSTM-TIA. The bandwidth of the proposed CryoSTM-TIA is still larger than 300 kHz. Its equivalent input noise current power spectral density is less than 30 (fA)2/Hz at 100 kHz. It is detailed, for quantum systems, by using the CryoSTM-TIA, how to measure scanning tunneling current spectra, scanning tunneling differential conductance spectra, and scanning tunneling noise current power spectra, in atomic scale, and then extract their scanning tunneling shot noise spectra. Thus, it is possible to study novel quantum phenomena in various quantum systems by measuring shot noise with the CryoSTM-TIA, such as the Andreev reflection in atomic scale, the Kondo effect in a single molecular magnet, and the existence of Majorana bound states, etc.
Subjects: Engineering and technical science >> Physics Related Engineering and Technology submitted time 2022-03-17
Abstract:
Global researchers have recently become interested in non-contact measurements of rocket motors, but the primary focus is on the rocket motor's temperature field or mechanical vibration. As a result, non-contact methods were seldom used to measure the exhaust velocity of the rocket motor. Traditional exhaust velocity measurements need complex equipment and have had few references for a lengthy time. Thus, a method for estimating the rocket motor sea-level exhaust velocity was offered, which makes use of the plume expansion angle measured in its image by integrating a one-dimensional compressible adiabatic flow model, the Prandtl-Mayer function in the ambient atmosphere, and the Brent algorithm. The relationship between the plume expansion angle and the sea-level exhaust velocity was determined in this study, and the results were compared to those obtained using the traditional method to verify the new method's accuracy. The estimation results showed that there was a linear relation between the sea-level exhaust velocity and the plume expansion angle, and the relative error compared to the tradition method is less than 2%. Therefore, it was shown this estimation method has a fairly good accuracy.
Peer Review Status:Awaiting Review