Terahertz Tomographic Atom Probe for Thermal-Free Field Evaporation
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Solution Overview
Problem
Current tomographic atom probes face challenges in achieving optimal analysis conditions for materials with large band gaps, particularly insulators and semiconductors, due to thermal effects from conventional ultraviolet or infrared laser pulses, leading to degraded mass resolution and composition biases, necessitating empirical adjustments and additional techniques for verification.
Innovation Solution
A tomographic atom probe utilizing terahertz pulses with a positively biased and cryogenically cooled nanotip, leveraging the antenna and resonant absorption effects to achieve field-effect evaporation without thermal influence, combined with a terahertz pulse generator and ion detector for precise analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If laser pulses in the near-UV range are used for evaporation, then fast evaporation mechanism is promoted for metals and semiconductors with small band gap, but absorption maxima occur far from the tip end for insulators and semiconductors with large band gap, giving rise to slow thermal evaporation that degrades mass resolution
Solution Approach 1:
The patent changes the fundamental parameter of evaporation mechanism from thermal to field-effect by using intense electric fields generated by terahertz pulses. This allows direct field-induced evaporation without relying on thermal effects, thereby achieving fast evaporation with high mass resolution for all material types including insulators and semiconductors with large band gaps
Solution Approach 2:
The patent replaces the optical-mechanical laser evaporation system with an electromagnetic field-based terahertz pulse system. The intense electric field from terahertz pulses directly induces field-effect evaporation, substituting the thermal mechanism of laser evaporation with a field-driven mechanism that works universally across different material types
2Speed
If strong static fields are applied to promote fast emission, then evaporation speed increases, but biases in composition measurements occur
Solution Approach 1:
The patent uses periodic terahertz pulses with specific timing and duration to induce field-effect evaporation. The pulsed nature allows control over the evaporation process, enabling fast emission while maintaining measurement accuracy by optimizing pulse parameters to avoid excessive field effects that cause composition biases
3Speed
If excessive field or laser energy values are used, then fast evaporation is achieved, but destruction of the sample occurs through electrostatic and thermal effects
Solution Approach 1:
The patent employs dynamic control of the electric field through terahertz pulses with adjustable duration, amplitude, and repetition rate. This dynamic approach allows optimization of evaporation speed while preventing sample destruction by keeping field parameters within safe limits, unlike static strong fields that inevitably lead to sample damage
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances mass resolution and widens the applicability to materials with large band gaps, including biological compounds, while increasing analysis success rates and reliability.
Implementation Method 1
the focusing of the terahertz pulses causing the atoms of the nanotip to evaporate through the field effect without thermal effects
Implementation Method 2
said nanotip being brought to a temperature of between 0 kelvin and ambient temperature by a cryogenic device
Implementation Method 3
Measuring the times of flight of the ions makes it possible to determine their chemical nature through time-of-flight mass spectroscopy
Implementation Method 4
The intense electric field thus created is sufficient to tear the atoms from the surface, which atoms are ionized and projected onto a position and time detector
Data Source
AI summary
A tomographic atom probe includes an analysis chamber intended to analyze a sample of material in the form of a nanotip mounted on an anti-vibration support, the nanotip being brought to a temperature of between 0 kelvin and ambient temperature, the nanotip being biased at an adjustable voltage of between 1 kV and 15 kV, the analysis chamber comprising a position-sensitive and time of flight-sensitive ion detector. The atom probe comprises a generator for generating high-peak-intensity single-cycle ultrashort terahertz pulses, the analysis chamber comprising optical means for focusing the terahertz pulses, the focusing of the terahertz pulses causing the atoms of the nanotip to evaporate through the field effect without thermal effects. The terahertz pulses are generated by a femtosecond pulsed laser emitting very high-power ultrashort optical pulses at a high rate.