XRD Doping Control of Light-Emitting cBN with a Large Size Mismatch between the Dopant and Intrinsic Atoms

At a Glance

Metadata	Details
Publication Date	2016-01-01
Journal	World Journal of Engineering and Technology
Authors	Е. М. Шишонок, V. G. Luhin, J. W. Steeds
Institutions	Belarusian State University, University of Bristol
Citations	4
Analysis	Full AI Review Included

XRD Doping Control in Wide Bandgap Materials: A 6CCVD Analysis

This technical documentation analyzes the research on Rare Earth (RE) doped Cubic Boron Nitride (cBN) and highlights how 6CCVD’s expertise in MPCVD diamond materials (the closest analog to cBN) can support and advance similar research in optoelectronics, quantum materials, and high-power applications.

Executive Summary

The following points summarize the key findings of the research paper regarding doping control and defect engineering in cBN, a material closely analogous to diamond:

Material Focus: Investigation of light-emitting Cubic Boron Nitride (cBN) doped with various Rare Earth (RE) elements (Eu, Tb, Er, Sm, Nd) synthesized via HPHT.
Optoelectronic Potential: cBN:RE micropowders exhibit intense discrete photoluminescence (PL) in the IR, red, and green spectral ranges, confirming their utility for next-generation light emitters and phosphors.
Defect Engineering: Eu³⁺ ions were conclusively shown to occupy two distinct, low-symmetry sites (Eu1, Eu2) within the cBN lattice, demonstrating the complexity of defect formation.
Structural Distortion: High-resolution XRD analysis revealed non-uniform crystalline distortion and the formation of disordered solid solutions due to the large atomic size mismatch between the RE dopants and the intrinsic B/N atoms.
Doping Control Methodology: The study successfully established XRD as a precise method for in situ doping control and structural analysis in cBN, a technique highly relevant for defect engineering in diamond.
Concentration Range: Successful incorporation of RE dopants was achieved in the critical range of < 0.01 at.% up to > 0.1 at.%, crucial for functional material properties.

Technical Specifications

The following hard data points were extracted from the experimental details and results:

Parameter	Value	Unit	Context
cBN Bandgap (E_g)	6.4	eV	Widest bandgap semiconductor in AIIIBV group
Incorporated RE Content Range	< 0.01 up to ~0.1	at. %	Concentration achieved in cBN crystal lattice
Volume Mean Diameter D(4,3)	3.5 - 5.5	µm	Grain size of cBN:RE micropowders
XRD Radiation Source	CuKα	N/A	Used for high-resolution diffraction analysis
XRD Recording Step	0.01	°/min	Precision of structural measurements
PL Excitation Wavelength (λ_exc)	488	nm	Used for Eu and Tb PL testing
PL Excitation Wavelength (λ_exc)	960	nm	Used for Er PL testing (⁴I_13/2 → ⁴I_11/2 transitions)
Annealing Temperature (T_ann)	870	K	Used to study Eu³⁺ ion redistribution
PL Measurement Temperature (T_reg)	300	K	Room Temperature (RT) testing
PL Emission Range (cBN:Tb)	700 - 900	nm	Broad band emission (multi-vacancy nature)

Key Methodologies

The research utilized a combination of high-pressure synthesis and advanced structural and optical characterization techniques:

High Pressure-High Temperature (HPHT) Synthesis: cBN:RE micropowders were manufactured via catalytic synthesis from hexagonal Boron Nitride (hBN) precursors in the presence of low-melting RE compounds (Er, Tb, Eu, Sm, Nd).
Dopant Quantification: Precursor and final incorporated RE concentrations were analyzed using XPS and RBS methods, confirming the low incorporation efficiency (< 0.1 at.%).
High-Resolution X-ray Diffraction (XRD): XRD patterns were collected using CuKα radiation with a high-precision recording step (0.01°/min) to analyze peak asymmetry, shifts, and extra-splits.
Structural Deconvolution: Computer programs were employed to deconvolute complex XRD peaks using Voigt profiles, which account for both particle-size broadening (Lorentzian) and strain broadening (Gaussian).
Photoluminescence (PL) Spectroscopy: PL spectra were measured at 300 K (Room Temperature) to identify discrete intra-electronic transitions of RE³⁺ ions, confirming the location and symmetry of luminescence centers (e.g., Eu1 and Eu2).
Defect Analysis: The appearance and characteristics of XRD extra-splits were analyzed in relation to RE ion size and concentration to deduce the mechanism of crystalline distortion and the formation of non-uniformly distorted solid solutions.

6CCVD Solutions & Capabilities

The research demonstrates the critical role of precise doping and defect engineering in wide bandgap semiconductors, a field where 6CCVD’s expertise in MPCVD diamond is directly applicable. Diamond (SCD) is the closest structural and electronic analog to cBN, and our capabilities are optimized to meet the stringent material requirements for similar optoelectronic and quantum applications.

Applicable Materials

To replicate or extend this research into the diamond platform, 6CCVD recommends the following materials:

Optical Grade Single Crystal Diamond (SCD): Required for applications demanding the highest purity, lowest strain, and superior optical transparency (UV to IR). Ideal for creating and studying isolated, controlled defects (e.g., NV centers, SiV centers) analogous to the RE³⁺ centers studied in cBN.
- Thickness Capability: 0.1 µm up to 500 µm.
- Polishing: Ultra-smooth surfaces with Ra < 1 nm.
Custom Boron-Doped Diamond (BDD): For research requiring controlled p-type conductivity or high-power electrode applications. Our MPCVD process allows for precise, uniform boron doping control.
Large-Area Polycrystalline Diamond (PCD): Suitable for scalable applications like high-power heat spreaders or large-area phosphors, offering plates/wafers up to 125mm in diameter.

Customization Potential

The paper highlights the necessity of precise structural control and integration. 6CCVD offers comprehensive customization services to accelerate device development:

Service	6CCVD Capability	Relevance to Research
Custom Dimensions	Plates/wafers up to 125mm (PCD); Substrates up to 10mm thickness.	Provides large-area platforms for scalable device manufacturing, moving beyond micropowders.
Precision Polishing	Ra < 1 nm (SCD); Ra < 5 nm (Inch-size PCD).	Essential for minimizing surface defects and intrinsic strain, critical for high-resolution PL/XRD analysis.
Custom Metalization	In-house deposition of Au, Pt, Pd, Ti, W, Cu stacks.	Enables direct integration of electrical contacts for high-field or optoelectronic devices, such as creating ohmic contacts on BDD or barrier layers on SCD.
Thickness Control	SCD and PCD layers available from 0.1 µm to 500 µm.	Allows researchers to optimize material thickness for specific optical path lengths or thermal management requirements.

Engineering Support

6CCVD’s in-house PhD team specializes in the growth and characterization of MPCVD diamond. We can assist researchers with similar defect engineering and wide bandgap optoelectronics projects by providing:

Material Selection Consultation: Guidance on choosing the optimal diamond grade (SCD vs. PCD, doping level, orientation) to minimize background defects and maximize target defect stability.
Doping Recipe Optimization: Support for achieving ultra-low or high concentrations of dopants (e.g., Nitrogen, Silicon, Boron) necessary for creating functional quantum or light-emitting centers, mirroring the precise concentration control demonstrated in the cBN study.
Structural Analysis Interpretation: Expertise in correlating growth parameters with resulting material strain and crystalline quality, directly addressing the XRD distortion analysis presented in the paper.

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

View Original Abstract

Cubic boron nitride (cBN) as the outstanding representative of the family of semiconducting wide bandgap nitrides and the closest analogue of diamond, is produced and investigated. XRD as method for doping control of cBN with impurities of large atomic sizes, is suggested. The larger an atomic size mismatch between doping and intrinsic atoms of a semiconductor’s crystal lattice, the stronger its response through own strains and distortions. The distortions are expected to be notable in the case of the smallest intrinsic atoms of cBN and diamond. The light-emitting cBN doped with various rare-earth elements (RE) in different concentrations under high pressure conditions is synthesized in form of the cBN: RE single phase micropowders. The micro-powders showed the discrete photoluminescence spectra in IR-, red and green spectral ranges which were attributed to the intra-electronic transitions of RE3+ ions located in cBN crystal lattice. The locations of the RE3+ ions in cBN crystal lattice are discussed. The data of XRD (CuKα) analysis of the cBN:RE micropowders are repre- sented. Extra-splits (as the additional ones to the α1-α2-splits on CuKα) of the cBN parent peaks in XRD patterns of the cBN: RE, are discovered and analyzed using appropriate computer programs. As established, crystal lattice of cBN due to the incorporation of RE3+ ions, represents a disordered solid solutions which are nonuniformly distorted in dependence on the ions’ size and their concentrations in cBN. Results of the present work can be useful to manufacture cBN with predictable functional properties, as well as for in situ doping control of cBN and diamond.

Tech Support

Original Source

DOI: https://doi.org/10.4236/wjet.2016.43d021