Diamond NV Centre Fabrication via Atomic-Scale Nitrogen Placement
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Solution Overview
Problem
The precision fabrication of arrays of nitrogen vacancies (NV) in diamond quantum computers is challenging due to the limitations of 'top-down' nitrogen ion-implantation techniques, which face issues with implantation mask fabrication and ion scattering.
Innovation Solution
A method involving a diamond substrate with a passivated surface, where passivation atoms are removed to create de-passivated sites, exposed to a nitrogen-containing compound to adsorb nitrogen, and then overgrown with diamond by chemical vapour deposition (CVD) to incorporate nitrogen as NV centres, which are subsequently charged with a negative charge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If top-down nitrogen ion-implantation techniques are used, then nitrogen can be introduced into diamond, but implantation mask fabrication and ion scattering cause poor manufacturing precision
Solution Approach 1:
The patent inverts the conventional top-down ion implantation approach by using bottom-up atomic-scale fabrication. Instead of implanting nitrogen ions into diamond, the method grows diamond around pre-positioned nitrogen atoms on the surface, achieving atomic precision without requiring complex implantation masks.
Solution Approach 2:
The process segments the nitrogen introduction and diamond growth into separate sequential steps: first positioning nitrogen atoms at precise locations on the diamond surface, then growing diamond around them. This segmentation eliminates the need for complex mask fabrication while maintaining atomic precision.
2Productivity
If CVD is optimized for maximum diamond growth rate, then productivity increases, but nitrogen diffusion and desorption occur reducing manufacturing precision
Solution Approach 1:
The patent uses periodic alternation between low-temperature growth conditions (to prevent nitrogen diffusion/desorption) and subsequent higher-temperature growth (to achieve final diamond quality). This periodic control of growth conditions maintains nitrogen precision while ultimately achieving high-quality diamond with acceptable growth rates.
Solution Approach 2:
The method changes key CVD parameters (temperature, pressure, gas composition) to specific ranges that suppress nitrogen diffusion and desorption during the critical early growth phase, while still enabling diamond formation. This parameter optimization resolves the contradiction between growth rate and nitrogen placement precision.
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
This method enables the accurate and repeatable fabrication of NV centres with atomic precision, essential for reliable inter-qubit coupling in diamond quantum computers, while avoiding diffusion or desorption of nitrogen during diamond growth.
Implementation Method 1
overgrowing the multiple de-passivated sites with diamond by chemical vapour deposition (CVD) at a diamond growth rate related to a temperature and a pressure
Implementation Method 2
exposing the multiple de-passivated sites to a nitrogen-containing compound to adsorb nitrogen at the multiple de-passivated sites of the diamond substrate
Data Source
AI summary
This disclosure relates to a method for manufacturing multiple optically addressable qubits in diamond. The method comprises providing a diamond substrate with a passivated surface; removing passivation atoms from the passivated surface to create multiple de-passivated sites where the passivation atoms have been removed; exposing the multiple de-passivated sites to a nitrogen-containing compound to adsorb nitrogen at the multiple de-passivated sites of the diamond substrate; overgrowing the multiple de-passivated sites with diamond by chemical vapour deposition (CVD) at a diamond growth rate related to a temperature and a pressure, wherein diffusion or desorption of the nitrogen at the multiple de-passivated sites is avoided to incorporate the nitrogen into the diamond; converting the incorporated nitrogen into multiple nitrogen vacancies; and charging the multiple nitrogen vacancies with a negative charge.