Development of planar microstrip resonators for electron spin resonance spectroscopy

Abstract

<jats:p>This work focuses on the development of planar microwave resonators for use in electron spin resonance spectroscopic studies. Two half-wavelength microstrip resonators of different geometrical shapes, namely straight ribbon and omega, are fabricated on commercially available microwave laminates. Both resonators have a characteristic impedance of 50 Ω. We have performed electromagnetic field simulations for the resonators and have extracted design parameters that were used for fabrication. The effect of the geometry on the quasi-transverse electromagnetic (quasi-TEM) modes of the resonators is noted from simulation results. The fabrication is done using optical lithography in which laser printed photomasks are used. This prototyping technique allows us to fabricate resonators in a few hours with accuracy up to 6 mils. The resonators are characterized using a Vector Network Analyzer. The fabricated resonators are used in a home built low-temperature continuous wave electron spin resonance (CW-ESR) spectrometer which operates in S-band. It captures the absorption spectrum of the free radical DPPH, at both room temperature and 77 K. The measured <jats:italic>g</jats:italic>-factor using our resonators is consistent with the values reported in literature. Spin sensitivity of 10<jats:sup>15</jats:sup> spins/gauss is achieved at 77 K. The designed resonators will be used in setting up a pulsed electron spin resonance spectrometer by suitably modifying the CW-ESR spectrometer.</jats:p>

Detection of electron spin resonance down to 10 K using localized spoof surface plasmon

“…In our previous studies [28,29], we had developed spectrometers based on planar transmission lines. These spectrometers had SNR values of ∼ 400.…”

“…The structure's fabrication is carried out using a rapid prototyping process employing optical lithography [28] followed by wet etching [29]. The detailed fabrication procedure has been listed in table 1.…”

Detection of electron spin resonance down to 10 K using localized spoof surface plasmon

“…The dielectric property of the teflon wrapped sample perturbs the electric field (figure 6) on the CMSS [19] leading to the shift in f res values at different temperatures. The signal to noise ratio (SNR) [32], [33] is around 46 at 10 K & 34 at 295 K. Spin sensitivity [34], [35] is about 10 16 spins/gauss for the sample used with a measured ESR line width of 3.36 G at 10 K. The LSSPR based ESR spectrometer has SNR value which is one order lower than the spectrometers developed by us [22], [23] that utilize planar transmission line based resonators in reflection geometry and consequently has spin sensitivity value which is one order higher.…”

“…The study is concluded in section 5, with a discussion on the potential application of the designed resonator in the detection of ESR transitions caused by a microwave Rashba field in low dimensional systems. 2 The Localized Spoof Surface Plasmonic Resonator The fabrication of the structure is carried out using a rapid prototyping process employing optical lithography [22] followed by wet etching [23]. SMA connectors are soldered at either end of the conducting trace for the propagation of microwave signal.…”

A short-circuited coplanar waveguide for low-temperature single-port ferromagnetic resonance spectroscopy set-up to probe the magnetic properties of ferromagnetic thin films

“…For a CPW with a characteristic impedance of 50 ohms, the line calculator calculated the width of the signal line and the gap to be 900 microns and 500 microns respectively. The fabrication is done using optical lithography which is described in detail in the literature [45]. Other components of our measurement system are a)Vector Network Analyser(VNA), which is a microwave source as well as a detector; b)the electromagnet that generates the external magnetic field, i.e., Zeeman field and; c)the optistat dry cryogen-free cooling system from Oxford instruments which is used for low-temperature measurements.…”