| Metadata | Details |
|---|
| Publication Date | 2020-06-04 |
| Journal | Processes |
| Authors | N. I. Polushin, Alexander I. Laptev, Đ. Đ. ХпОŃŃĐœ, A.E. Alexenko, Alexander Mihailovich Polyansky |
| Institutions | National University of Science and Technology, Frumkin Institute of Physical Chemistry and Electrochemistry |
| Citations | 22 |
| Analysis | Full AI Review Included |
- Novel Doping Strategy: A Chemical Vapor Deposition (CVD) process was developed for growing heavily boron-doped single-crystal diamond films using Triethyl Borate (TEB, (C2H5O)3B) as the boron precursor, replacing highly toxic and unstable Diborane (B2H6).
- In-Situ Defect Etching: The oxygen atoms inherent in the TEB molecule enable simultaneous diamond deposition and continuous, in-situ etching of polycrystalline defects and non-diamond carbon.
- Process Stability and Homogeneity: This continuous etching eliminates the need for process interruption, solving the problem of structural inhomogeneity and allowing for stable, high-quality epitaxial growth.
- High Doping Level Achieved: The resulting monocrystalline layers achieved a stable, high boron concentration of 2.9% (mass).
- Structural Quality: The films exhibited single-crystal epitaxial growth, confirmed by Electron Backscatter Diffraction (EBSD), with no diamond polycrystals detected on the surface or periphery.
- Exceptional Mechanical Properties: The deposited films demonstrated high mechanical performance, with Hardness ranging from 62 to 117 GPa and Elastic Modulus between 914 and 1099 GPa.
| Parameter | Value | Unit | Context |
|---|
| Substrate Temperature | 1100 | °C | Optimal synthesis mode |
| Reactor Pressure | 9.806 | kPa | Optimal synthesis mode |
| Microwave Power | 3800 | W | Optimal synthesis mode |
| Deposited Layer Thickness | ~8 | ”m | Monocrystalline layer |
| Deposition Rate | 4 | ”m/h | Achieved growth rate |
| Boron Content (Mass %) | 2.9 | % | Stable concentration in doped films |
| Hardness (H) Range | 62 to 117 | GPa | Measured via Oliver-Farr method |
| Elastic Modulus (E) Range | 914 to 1099 | GPa | Measured via Oliver-Farr method |
| H2 Flow Rate (Total) | 480 | cm3/min | Optimal synthesis mode |
| CH4 Flow Rate | 25 | cm3/min | Optimal synthesis mode |
| H2 - (C2H5O)3B Flow Rate | 10 | cm3/min | Dopant stream flow rate |
| Dopant Bubbler Temperature | 25 ± 1 | °C | Maintained constant for stable gas composition |
- Substrate Preparation: Single-crystal diamond substrates were prepared using standard methods (etching, laser cutting, mechanical treatment). Etching was performed in plasma (e.g., H2, O2-Ar, or O2-H2) to clean the surface prior to deposition.
- Triethyl Borate (TEB) Synthesis: TEB ((C2H5O)3B) was generated by mixing excess boric acid (99.9% purity) with ethyl alcohol (95% aqueous solution) in a bubbler system.
- Dopant Delivery System: The TEB bubbler was placed in a thermostat maintained at 25 °C to ensure constant vapor pressure. High-purity H2 (99.9995%) was split; a small stream (10 cm3/min) passed through the bubbler to carry the volatile TEB into the reactor, while the main H2 stream bypassed it.
- Gas Mixture Composition: The deposition gas phase consisted of Methane (CH4), Hydrogen (H2), and Triethyl Borate (TEB). The high concentration of TEB was initially used to ensure sufficient oxygen for etching defects.
- Simultaneous Etching and Deposition: Oxygen atoms released from the TEB molecule provided continuous, in-situ etching of emerging polycrystalline diamond and non-diamond carbon, maintaining a high-quality epitaxial growth front without process interruption.
- CVD Growth: Films were grown for 2 hours at 1100 °C and 9.806 kPa pressure using 3800 W microwave power.
- Characterization: Surface morphology and defect analysis were performed using Scanning Electron Microscopy (SEM). Elemental composition (Boron content) was determined via Energy-Dispersive X-ray Spectroscopy (EDS). Crystallinity and orientation were confirmed as single-crystal epitaxial growth using EBSD. Mechanical properties (Hardness and Elastic Modulus) were measured using the Oliver-Farr method via nanoindentation.
- Power Electronics: Boron-doped diamond (BDD) is a critical semiconductor material for high-power, high-frequency, and high-temperature devices (e.g., diodes and transistors) due to its wide bandgap and high carrier mobility.
- Advanced Sensors: BDD films are used in electroanalytical applications, including chemical sensors and biosensors, owing to their chemical inertness and wide potential window.
- Radiation Detection: Potential use in neutron detectors, particularly when coupled with graphitic electrodes, leveraging diamondâs stability.
- Jewelry Industry: The ability to grow thick, homogeneous, doped layers serves as rough material for cutting fancy-colored (blue) diamonds, reducing production costs compared to growing thin films for semiconductor use.
- Microelectromechanical Systems (MEMS): Utilization of BDDâs extreme hardness and high elastic modulus for durable, high-performance micro-components.
View Original Abstract
Boron-doped diamond is a promising semiconductor material that can be used as a sensor and in power electronics. Currently, researchers have obtained thin boron-doped diamond layers due to low film growth rates (2-10 ÎŒm/h), with polycrystalline diamond growth on the front and edge planes of thicker crystals, inhomogeneous properties in the growing crystalâs volume, and the presence of different structural defects. One way to reduce structural imperfection is the specification of optimal synthesis conditions, as well as surface etching, to remove diamond polycrystals. Etching can be carried out using various gas compositions, but this operation is conducted with the interruption of the diamond deposition process; therefore, inhomogeneity in the diamond structure appears. The solution to this problem is etching in the process of diamond deposition. To realize this in the present work, we used triethyl borate as a boron-containing substance in the process of boron-doped diamond chemical vapor deposition. Due to the oxygen atoms in the triethyl borate molecule, it became possible to carry out an experiment on simultaneous boron-doped diamond deposition and growing surface etching without the requirement of process interruption for other operations. As a result of the experiments, we obtain highly boron-doped monocrystalline diamond layers with a thickness of about 8 ÎŒm and a boron content of 2.9%. Defects in the form of diamond polycrystals were not detected on the surface and around the periphery of the plate.
- 2010 - Effect of B/C ratio on the physical properties of highly boron-doped diamond films [Crossref]
- 2020 - Voltammetric characterization of boron-doped diamond electrodes for electroanalytical applications [Crossref]
- 2020 - Preparation of boron-doped diamond foam film for supercapacitor applications [Crossref]
- 2017 - Evidence of linear Zeeman effect for infrared intracenter transitions in boron doped diamond in high magnetic fields [Crossref]
- 2016 - Optical and electrical properties of boron doped diamond thin conductive films deposited on fused silica glass substrates [Crossref]
- 2013 - Electrical properties of the high quality boron-doped synthetic single-crystal diamonds grown by the temperature gradient method [Crossref]
- 2015 - Properties of boron-doped epitaxial diamond layers grown on (110) oriented single crystal substrates [Crossref]
- 2017 - Thin CVD diamond film detector for slow neutrons with buried graphitic electrode [Crossref]
- 2017 - Investigations of the co-doping of boron and lithium into CVD diamond thin films [Crossref]
- 2015 - Low resistivity p+ diamond (100) films fabricated by hot-filament chemical vapor deposition [Crossref]