Electron spin resonance spectrometer and method for using same
Inventors
CAMPBELL, JASON P. • Cheung, Kin P. • Ryan, Jason T • Lenahan, Patrick M.
Assignees
Penn State Research Foundation • National Institute of Standards and Technology NIST • United States Department of Commerce
Publication Number
US-9507004-B2
Publication Date
2016-11-29
Expiration Date
2034-04-03
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Abstract
An electron spin resonance spectrometer includes a bridge to transmit an excitation frequency and to receive a signal frequency; a probe electrically connected to the bridge and comprising: a first conductor in electrical communication with the bridge to transmit the signal frequency to the bridge; a shorting member electrically connected to the first conductor to transmit the excitation frequency to a sample, to produce the signal frequency, and to transmit the signal frequency to the first conductor; and a second conductor electrically connected to the shorting member; and a magnet disposed proximate to the probe.
Core Innovation
The invention is an electron spin resonance spectrometer comprising a bridge to transmit an excitation frequency and receive a signal frequency, a probe electrically connected to the bridge that includes a first conductor to transmit the signal frequency to the bridge, a shorting member electrically connected to the first conductor to transmit the excitation frequency to a sample, produce the signal frequency, and transmit the signal frequency back to the first conductor, a second conductor electrically connected to the shorting member, and a magnet disposed proximate to the probe. The probe can be a surface scanning probe or a near-field probe, operating without a resonant cavity, thereby enabling high resolution spectroscopic characterization of atomic-scale defects with nanoscale spatial resolution.
The problem being addressed arises from the continued miniaturization of microelectronic devices, specifically MOSFETs, where atomic-scale defects critically impact device performance and reliability. Conventional characterization methods are inadequate for understanding these defects at the atomic scale, impeding further scaling and development of microelectronics. Random telegraph noise and drive current fluctuations in nanoscale MOSFETs highlight the need for detailed spectroscopic knowledge of these defects. Thus, improved methods and equipment for atomic-scale defect characterization are needed to overcome existing limitations.
The electron spin resonance spectrometer overcomes deficiencies by providing spectroscopic information without a cavity, allowing flexibility in sample size and geometry. It employs a bridge with balanced arms and a shorting member-based probe to transmit and detect excitation and signal frequencies, enabling detection of resonant absorption by unpaired electrons in samples. The system supports continuous wave and pulsed modes and uses homodyne or superheterodyne detection. The magnet and modulation coil apply and modulate magnetic fields to the sample externally, facilitating electron spin resonance transitions. This arrangement enables spatially selective detection of unpaired electrons with high sensitivity and resolution.
Claims Coverage
The patent includes a set of independent claims that cover the main inventive features related to the electron spin resonance spectrometer and its components, the shorting member structure, and the method for acquiring electron spin resonance spectra.
Electron spin resonance spectrometer with specific probe and magnet configuration
An electron spin resonance spectrometer comprising a bridge to transmit an excitation frequency and receive a signal frequency, a probe electrically connected to the bridge including a first conductor, a shorting member electrically connected to the first conductor to transmit the excitation frequency to a sample and produce the signal frequency, a second conductor electrically connected to the shorting member, and a magnet disposed proximate to the probe.
Bridge with balanced and unbalanced states and detection system
A bridge comprising a reference arm, a sample arm with a circulator, and a combiner configured to be balanced in absence of the signal frequency and unbalanced in its presence, producing a combined frequency transmitted towards a detector, optionally including a local oscillator arm with a mixer to produce a detection frequency for the detector, and using a phase sensitive detector.
Shorting member as a lumped circuit with probe tip
The shorting member configured as a lumped circuit including first and second conductor extensions connected to respective conductors and a probe tip electrically shorting the first conductor to the second conductor, with the probe tip configured to transmit the excitation frequency to the sample.
Method for acquiring electron spin resonance spectrum
A method comprising disposing a sample external to the probe, magnet, and modulation coil in an electron spin resonance spectrometer comprising a bridge, probe, detector, magnet, and a modulation coil interposed between magnet and sample; transmitting an excitation frequency to the sample through the sample arm and shorting member; modulating the magnetic field at the sample through the modulation coil; allowing the sample to absorb the excitation frequency and produce a signal frequency; transmitting the signal frequency toward the detector; combining signal and excitation frequencies to produce a detection frequency; and detecting the detection frequency as a function of changing excitation frequency or magnetic field strength to acquire the electron spin resonance spectrum.
The independent claims cover the innovative electron spin resonance spectrometer structure with a shorting member probe and magnet arrangement, a bridge system enabling balanced detection, the lumped circuit shorting member with probe tip design, and the method for acquiring the electron spin resonance spectrum involving modulated magnetic fields and signal detection external to the probe assembly.
Stated Advantages
High sensitivity and high resolution spectroscopic characterization of atomic-scale defects with nano-scale spatial resolution.
Operation without a resonant cavity, allowing flexible sample sizes and geometries.
Supports both continuous wave and pulsed excitation modes with immediate detection.
Capability for spatially selective detection and surface scanning.
High acquisition speed, low noise, and potential miniaturization or portability.
Configuration yielding a quality factor approximately unity, indicating efficient energy transmission without storage.
Documented Applications
Characterization of atomic-scale defects in microelectronic devices such as MOSFETs to understand their physical and chemical nature.
Surface scanning and spatially resolved electron spin resonance spectroscopy of solid and fluid samples including defect centers and spin-containing molecules.
Acquisition of electron spin resonance spectra of solid crystalline samples, described with methyltriphenyl-arsonium tetracyanoquinodimethane and 2,2-diphenyl-1-picrylhydrazyl.
Electron spin resonance spectroscopy of liquid samples, exemplified with 2,2,6,6-tetramethyl-1-piperidinyloxy dissolved in ethylene glycol.
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