Monolayer TMDC Growth Using Pulsed Sulfurization and Sublimation
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Solution Overview
Problem
Existing methods for growing wafer-sized, highly uniform, and strictly monolayer transition metal dichalcogenides (TMDCs) are challenging due to uncontrollable growth kinetics, leading to inconsistent quality and misaligned grain orientations, which degrade the physical properties of the films, making them unsuitable for commercial applications.
Innovation Solution
A method involving the deposition of transition metals or their oxides on a substrate, followed by the introduction of a chalcogen precursor in the presence of an etching gas and carrier gas, and subsequent sublimation with a pulsating supply of chalcogen vapor to form a monolayer TMDC, utilizing a pulsating supply of chalcogen vapor to control growth and remove excess layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If traditional sulfurization process is used with sulfur powder in CVD furnace, then large-area growth of continuous TMDC thin films can be achieved, but the growth kinetics become uncontrollable and film quality becomes inconsistent
Solution Approach 1:
The patent changes the physical state of sulfur precursor from solid powder to liquid form, and controls its vapor pressure through temperature parameters. This allows precise control of sulfur supply rate by adjusting temperature, thereby achieving controllable growth kinetics and uniform monolayer formation across large areas
Solution Approach 2:
The patent replaces the mechanical/physical process of heating solid sulfur powder (which has uncontrollable evaporation) with a controlled liquid precursor system where sulfur supply is regulated through vapor pressure control and flow rate management, enabling precise deposition control
2Manufacturing precision
If MOCVD process with liquid precursors is used, then precursor supply can be controlled reliably, but growth time becomes excessively long and grain size remains small
Solution Approach 1:
The patent employs periodic pulsing of sulfur precursor vapor supply during the deposition process. This periodic action creates controlled growth cycles that promote faster grain coalescence and larger grain size formation while maintaining precise precursor supply control, significantly reducing overall growth time
Solution Approach 2:
The patent introduces dynamic control of sulfur vapor flow rate during deposition, adjusting the supply conditions in real-time to optimize growth kinetics. This dynamic adjustment enables faster growth rates while maintaining monolayer quality and achieving larger grain sizes
3Area of stationary object
If continuous sulfur vapor supply is used during growth, then continuous TMDC film can be formed, but excess layers and bilayer domains are created
Solution Approach 1:
The patent uses periodic pulsing of sulfur precursor vapor rather than continuous supply. This periodic action allows controlled formation of monolayer domains before stopping sulfur supply, preventing excessive growth and bilayer formation while ensuring continuous film coverage through controlled grain coalescence
Solution Approach 2:
The patent applies controlled sulfur supply that is sufficient to complete monolayer formation but stops before excess layers can form. By carefully controlling the duration and amount of sulfur exposure, the process achieves complete coverage without over-growth
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 achieves a highly uniform, aligned, and reproducible monolayer TMDC film with improved electrical mobility, suitable for industrial applications, by controlling the growth process to ensure a single layer without misalignment, thus enhancing the reliability and scalability of TMDC films.
Implementation Method 1
subliming the transition metal dichalcogenide on the substrate in the presence of a pulsating supply of a vapor of the chalcogen precursor
Implementation Method 2
introducing a chalcogen precursor to the transition metal, the transition metal oxide, or the mixture thereof, in the presence of an etching gas
Data Source
AI summary
A method for forming a transition metal dichalcogenide monolayer, which includes depositing a transition metal, a transition metal oxide, or a mixture thereof, on a substrate, introducing a chalcogen precursor to the transition metal, the transition metal oxide, or the mixture thereof, in the presence of an etching gas and a carrier gas at a first temperature, to form a transition metal dichalcogenide on the substrate from the transition metal, the transition metal oxide, or the mixture thereof, and subliming the transition metal dichalcogenide on the substrate in the presence of a pulsating supply of a vapor of the chalcogen precursor to form the transition metal dichalcogenide monolayer at a second temperature, wherein the vapor of the chalcogen precursor comprises a chalcogen vapor.