Quantum Dot Microscope Probe with Tapered Tip for Strong Coupling

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Solution Overview

Problem

Traditional near-field Scanning Single Electron Transistor Microscopes (SSETMs) are sensitive to surface interactions due to delicate tunnel junctions, requiring a 50-200 nm distance from the sample, which limits strong coupling and often damages the probe, while conventional optical fiber probes cannot achieve close proximity to the specimen.

Innovation Solution

A quantum dot microscope apparatus with a tilted or tapered probe tip, featuring a quantum dot or nanoscale semiconductor with one tunneling lead connected to a power source and multiple capacitive leads, allowing for strong coupling and positioning the quantum dot as close as 0.5 nm to the sample surface while protecting the tunnel junction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If the probe is positioned close to the sample surface (0.5 nm) to achieve strong coupling, then the interaction strength with electronic states is improved, but the delicate tunnel junction is damaged by surface contact

Engineering Contradiction:

Improveinteraction strengthVSAvoidprobe durability

Core Design Contradiction:

ForceVSReliability

Solution Approach 1:

The probe is segmented into functionally distinct regions: a robust tunnel junction positioned away from the sample surface and a quantum dot positioned close to the sample surface. This segmentation allows each component to perform its optimal function without compromising the other - the tunnel junction maintains reliability while the quantum dot achieves strong coupling with the sample.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The probe employs an asymmetric configuration where the tunnel junction and quantum dot are positioned at different distances from the sample surface. The tunnel junction is positioned farther away to avoid damage, while the quantum dot is positioned closer to achieve strong coupling. This asymmetric arrangement resolves the contradiction by allowing different parts of the system to operate at different distances simultaneously.

Inventive Principle:

Principle #4Asymmetry

2Reliability

If the probe is positioned 50-200 nm away from the sample to protect the tunnel junction, then the probe durability is improved, but the coupling strength with the sample is reduced

Engineering Contradiction:

Improveprobe durabilityVSAvoidcoupling strength

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The quantum dot serves as an intermediary between the tunnel junction and the sample surface. It is positioned close to the sample to achieve strong coupling, while the tunnel junction remains positioned away from the sample to avoid damage. The quantum dot mediates the interaction, allowing strong coupling to be achieved without compromising tunnel junction durability.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of manufacture

If conventional optical fiber probes with flat apertures are used, then the manufacturing is simplified, but the probe cannot achieve close proximity to the specimen

Engineering Contradiction:

Improveprobe fabricationVSAvoidprobe-sample distance

Core Design Contradiction:

Ease of manufactureVSLength of moving object

Solution Approach 1:

Inventive Principle:

Principle #4Asymmetry

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

Enables robust probe interactions with the sample surface, achieving strong-coupling and single electron counting capabilities while protecting the tunnel junction, allowing for angstrom-distance tunneling and improved accuracy in electronic state measurements.

Implementation Method 1

A quantum dot or nanoscale semiconductor with only one tunneling lead connected to a power source

Methodology Applied

Scientific EffectSingle electron tunneling:

Implementation Method 2

two or more of the leads may be capacitive leads used to measure a quantum dot's thermodynamic density of states

Methodology Applied

Scientific EffectCapacitive coupling: Capacitance

Data Source

PatentUS11693024B2Quantum dot microscope apparatus comprising a nanoscale semiconductor on the tip of a fiber, a tunneling electrical lead and a capacitive electrical lead on the fiber

Publication Date: 2023.07.04 BOARD OF TRUSTEES OPERATING MICHIGAN STATE UNIV

AI summary

A quantum dot microscope apparatus is provided. A further aspect employs a tilted or tapered end or tip on a microscopic probe. Another aspect of the present apparatus employs a probe including a quantum dot with only one tunneling lead connected to a power source. A manufacturing aspect includes creating a tapered or asymmetrically shaped specimen-facing end of a probe where a quantum dot is located on the end. A further manufacturing aspect includes using focused ion-beam milling to create a tip or end of a quantum dot microscope probe.