Theoretical Studies of the Adsorption and Migration Behavior of Boron Atoms on Hydrogen-Terminated Diamond (001) Surface

At a Glance

Metadata	Details
Publication Date	2017-04-27
Journal	Coatings
Authors	Xuejie Liu, Congjie Kang, Haimao Qiao, Yuan Ren, Xin Tan
Institutions	Inner Mongolia University of Science and Technology
Citations	9
Analysis	Full AI Review Included

Technical Documentation: Boron Adsorption & Migration on H-Terminated Diamond (001)

Analysis for Advanced B-Doped Diamond (BDD) Growth Research

This document analyzes the research detailing the fundamental mechanism of boron incorporation into hydrogen-terminated diamond (001) surfaces via first-principles calculations. These insights are crucial for optimizing the Chemical Vapor Deposition (CVD) growth and electrochemical performance of Boron-Doped Diamond (BDD) films.

Executive Summary

This study, utilizing Density Functional Theory (DFT), provides critical validation of the atomic-level mechanisms that govern boron incorporation during MPCVD growth of BDD films.

Radical Site Dependence: Boron adsorption is highly dependent on the presence of open radical sites. Adsorption energy increases dramatically from a maximum of 1.387 eV (fully H-terminated surface) to up to 5.94 eV on surfaces with open radical sites (1ORS or 2ORS), confirming stable B incorporation at these active sites.
Surface Mobility: On a fully hydrogen-terminated diamond (001) surface, the boron atom migration barrier is low (1.216 eV), suggesting easy surface mobility and migration across the surface at typical CVD deposition temperatures (700-900 °C).
BH Radical Formation: The mechanism is validated where a boron atom abstracts a surface hydrogen atom, forming a stable BH radical and simultaneously creating a new radical site, which significantly influences the subsequent growth kinetics and doping profile.
Microstructure Control: The research confirms that the number and distribution of open radical sites directly influence the adsorption and migration of boron, providing a theoretical foundation for microstructural and electrochemical control in BDD synthesis.
6CCVD Value Proposition: 6CCVD provides the necessary ultra-pure, highly stable Polycrystalline (PCD) and Single Crystal Diamond (SCD) (001) substrates, crucial for experimental verification of these high-fidelity DFT models and for scaling BDD applications.

Technical Specifications

Extracted physical constants and critical energy parameters derived from the first-principles calculations.

Parameter	Value	Unit	Context
Adsorption Energy (Max)	1.387	eV	Fully H-terminated (001) surface
Adsorption Energy (Max)	5.936	eV	2ORS-R configuration (Two Open Radical Sites, Dimer Row)
Migration Barrier (Min, B atom)	1.216	eV	Fully H-terminated (001) surface, P5 to P1 path
Migration Barrier (Min, BH radical)	0.740	eV	2ORS-R configuration (P3 to P5 path)
Carbon-Hydrogen Bond Length	0.102	nm	Relaxed H-terminated diamond (001) surface
Dimer Bond Length (Relaxed)	0.162	nm	Reconstructed H-terminated diamond (001) surface
Diamond Lattice Constant (Calculated)	0.3568	nm	Optimized diamond crystalline structure
Covalent Radius Sum (B + C)	0.165	nm	Reference bond length for stable B-C bonding
Typical CVD Temperature Range	700-900	°C	Temperature range where B atom migration is easy
DFT Cut-Off Energy	350	eV	Plane-wave basis set energy
Electron Convergence Precision	10^-4	eV	Relaxation precision for electronic calculations

Key Methodologies

The theoretical investigation used established high-fidelity first-principles methods to simulate the BDD growth environment.

Computational Framework: All calculations were performed using the Vienna Ab-Initio Simulation Package (VASP 5.2), based on Density Functional Theory (DFT).
Basis Set and Approximation: The Projector-Augmented Wave (PAW) method was employed for electronic interactions, coupled with the Generalized Gradient Approximation (GGA) based on the Perdew-Burke-Ernzerhof (PBE) formulation.
Slab Model Construction: A large, multi-layer hydrogen-terminated diamond (001) slab was utilized, configured as 4 × 4 × (8 + 1 + 8). This model consisted of eight carbon layers (with 16 C atoms per plane), one hydrogen layer, and eight vacuum layers (~0.8020 nm height) to prevent periodic interference.
Simulation Constraints: The three bottom layers of carbon atoms were fixed during relaxation, while all other surface and adsorption atoms were allowed to move freely.
Adsorption Site Analysis: Boron adsorption energies (E_ad) were calculated across six highly symmetrical positions (P1-P6) on three primary surface types:
- Fully hydrogen-terminated.
- One Open Radical Site (1ORS).
- Two Open Radical Sites (2ORS-R, 2ORS-CO, 2ORS-CC).
Migration Path Determination: Minimum energy paths and corresponding energy barriers (E_a) for B atom and BH radical migration were calculated using the Nudged Elastic Band (NEB) method integrated into the VASP code.

6CCVD Solutions & Capabilities

This research confirms that the successful formation and microstructural stability of BDD films rely fundamentally on precise surface preparation and the controlled kinetics of boron adsorption. 6CCVD is uniquely positioned to supply the foundational and customized diamond materials required to experimentally replicate and advance these theoretical studies.

Applicable Materials

To replicate or extend this research into functional device fabrication, material engineers require diamond substrates with highly specific crystal orientations and exceptional purity.

6CCVD Material	Relevance to Research	Key Specification Alignment
Boron-Doped Diamond (BDD)	Direct application of findings to electrochemical devices, sensors, and micro-electromechanical systems (MEMS).	Custom B/C ratio and doping profiles, enabling researchers to correlate theoretical radical-site density with measurable film properties.
Optical Grade SCD (001)	Baseline for high-fidelity studies requiring atomically flat surfaces and defect densities lower than bulk PCD. The study specifically models the (001) plane.	Available in (001) orientation; Ra < 1nm polishing for ultimate surface control essential for radical site preparation.
High Purity PCD Wafers	Cost-effective and scalable substrates for BDD growth experiments and large-area deposition validation.	Custom dimensions up to 125mm diameter for scaling BDD manufacturing. Post-growth polishing to Ra < 5nm.

Customization Potential

The theoretical abstraction and radical creation mechanisms suggest that highly controlled surface patterning could revolutionize BDD growth. 6CCVD supports this advanced customization:

Precision Substrate Preparation: We supply diamond substrates (SCD and PCD) with verified crystallographic orientation, crucial for maintaining the stability of the H-termination layer and radical sites modeled in this paper.
Custom Metalization & Contacts: If researchers seek to test BDD films as electrochemical or electronic components, 6CCVD offers in-house metalization services, including common high-stability contacts required for diamond devices (Au, Pt, Pd, Ti, W, Cu).
Advanced Shaping: 6CCVD provides custom laser cutting and etching services to create precise geometric structures or define active areas, potentially enabling the fabrication of patterned radical sites for controlled doping.
Broad Thickness Range: Substrates and BDD active layers can be supplied from 0.1 µm up to 500 µm, giving maximum flexibility for creating thin-film BDD electrodes or thick, mechanical-grade layers.

Engineering Support

Understanding the complex interplay between surface dynamics (radical sites, migration barriers) and bulk properties is essential for maximizing BDD performance. 6CCVD’s in-house PhD engineering team possesses deep expertise in MPCVD growth kinetics and material characterization. We can assist researchers in selecting the optimal diamond substrate material, polishing grade, and initial doping concentration necessary for maximizing BDD uniformity and stability in applications like electro-synthesis, advanced biosensing, and electrochemical energy technology.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

The adsorption and migration activation energies of boron atoms on a hydrogen-terminated diamond (001) surface were calculated using first principles methods based on density functional theory. The values were then used to investigate the behavior of boron atoms in the deposition process of B-doped diamond film. On the fully hydrogen-terminated surface, the adsorption energy of a boron atom is relatively low and the maximum value is 1.387 eV. However, on the hydrogen-terminated surface with one open radical site or two open radical sites, the adsorption energy of a boron atom increases to 4.37 eV, and even up to 5.94 eV, thereby forming a stable configuration. When a boron atom deposits nearby a radical site, it can abstract a hydrogen atom from a surface carbon atom, and then form a BH radical and create a new radical site. This study showed that the number and distribution of open radical sites, namely, the adsorption of hydrogen atoms and the abstraction of surface hydrogen atoms, can influence the adsorption and migration of boron atoms on hydrogen-terminated diamond surfaces.

Tech Support

Original Source

DOI: https://doi.org/10.3390/coatings7050057

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