Carrier transport characteristics of H-terminated diamond films prepared using molecular hydrogen and atomic hydrogen

At a Glance

Metadata	Details
Publication Date	2017-06-28
Journal	International Journal of Minerals Metallurgy and Materials
Authors	Jinlong Liu, Liangxian Chen, Yuting Zheng, Jingjing Wang, Zhihong Feng
Institutions	University of Science and Technology Beijing, Hebei Semiconductor Research Institute
Citations	9
Analysis	Full AI Review Included

Technical Documentation & Sales Analysis: H-Terminated Diamond Carrier Transport

This document analyzes the research paper, “Carrier transport characteristics of H-terminated diamond films prepared using molecular hydrogen and atomic hydrogen,” to provide key technical takeaways and align the findings with the advanced material supply and engineering capabilities of 6CCVD.

Executive Summary

The research confirms that the method of H-termination is critical to achieving stable, high-performance p-type surface conductivity in diamond films, a key requirement for high-frequency and high-power electronic devices.

Atomic Hydrogen Superiority: Treatment using Microwave (MW) hydrogen plasma (generating active atomic H) yields significantly superior and more stable carrier transport characteristics compared to thermal hydrogenation (molecular H).
Performance Metrics: Plasma-treated films exhibited stable carrier mobility (15 cm² V^-1 s^-1) and a high carrier density (> 5 x 10¹² cm^-2).
Stability Confirmation: Plasma treatment resulted in sheet resistance two orders of magnitude lower (6 x 10⁴ - 8 x 10⁴ Ω) than thermally treated films (1 x 10⁶ - 2.5 x 10⁶ Ω).
Mechanism of Improvement: Activated atomic hydrogen restructures the diamond surface via an etching effect, effectively removing polishing-induced defects (scratches/burrs) and passivating electrically active surface states.
Instability Risk: Thermal hydrogenation resulted in highly variable carrier mobility (2 to 33 cm² V^-1 s^-1) due to the retention of surface defects from polishing, which act as scattering and trapping centers.
Implication for Devices: Achieving low roughness and precise, defect-free surface termination is crucial for manufacturing reliable H-terminated diamond Field-Effect Transistors (FETs).

Technical Specifications

The following hard data points extracted from the research highlight the performance differential between the two hydrogenation methods:

Parameter	Atomic H Plasma Treatment (15 min)	Molecular H Thermal Treatment (1 h)	Unit	Context
Carrier Mobility (μ)	15 (Highly Stable)	2 to 33 (Highly Variable)	cm² V^-1 s^-1	Measured at five different points
Carrier Density	> 5 x 10¹²	~1 order of magnitude lower	cm^-2	Measured using van der Pauw-Hall method
Sheet Resistance (R_s)	6 x 10⁴ to 8 x 10⁴	1 x 10⁶ to 2.5 x 10⁶	Ω	Two orders of magnitude higher for thermal
Surface Roughness (Ra)	0.6	nm	~0.3 (in 1 µm x 1 µm area)	Lowest achieved after plasma treatment
Thermal Treatment Recipe	N/A	800 °C, 5 kPa H₂ atmosphere	°C, kPa	Used a resistance furnace
Ohmic Contact Resistance	< 10^-5	< 10^-5	Ω·cm²	Achieved with non-annealed Au contacts (TLM)

Key Methodologies

The experiment compared two methods for H-termination on high-quality, polished diamond films grown by Direct Current (DC) arc jet CVD:

Initial Preparation (Common to both samples):
- Substrate Quality: High-quality diamond films were polished using a polycrystalline diamond disk to achieve a roughness (Ra) < 5 nm.
- Sizing: Films were laser-cut into 15 mm x 15 mm squares.
- Cleaning (Oxidation): Samples were boiled in H₂SO₄:HNO₃ (5:1 volume ratio) to remove non-diamond carbon and induce oxygen termination (C=O bonding).
- Final Rinse: Ultrasonic cleaning in deionized water, acetone, and ethanol. Samples stored in ethanol until use.
Hydrogen Plasma Treatment (Atomic H):
- Process: Samples placed in a microwave (MW) chamber.
- Recipe: Hydrogen plasma applied for a total treatment time of 15 minutes.
- Result: Surface restructuring, removal of scratches/burrs, and surface state passivation via etching effect.
Thermal Hydrogenation (Molecular H):
- Equipment: Resistance furnace under a protective hydrogen atmosphere.
- Recipe: Samples heated to 800 °C under 5 kPa of flowing hydrogen gas for 1 hour.
- Result: Simple C=O conversion to C-H bonding; polishing defects and surface states remained unpassivated.
Characterization:
- Electrical: Surface conductivity via van der Pauw-Hall tests using Au ohmic contacts, with conductivity homogeneity evaluated across five random points (100 µm x 100 µm test area).
- Surface Chemistry: Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FT-IR) confirmed C-H termination and the disappearance of C=O bonds.

6CCVD Solutions & Capabilities

This research demonstrates that stable, high-performance H-terminated diamond devices rely critically on two factors: the quality of the starting material (low defects, excellent polish) and precision control over the surface treatment process (atomic hydrogen/plasma etching). 6CCVD’s advanced MPCVD growth and post-processing capabilities are engineered to meet these exact requirements for high-frequency and high-power applications.

Material Recommendations for H-Termination Research

Application Requirement	6CCVD Applicable Material	Engineering Specification
Replication of Study	Polycrystalline Diamond (PCD)	High-quality material suitable for large area production, available in plates/wafers up to 125 mm. Thickness: 0.1 µm - 500 µm.
Maximum Electronic Stability	Optical Grade Single Crystal Diamond (SCD)	SCD offers superior intrinsic purity and low defect density, minimizing bulk scattering centers and maximizing carrier mobility potential prior to surface termination. Thickness: 0.1 µm - 500 µm.
Low Surface Roughness (Initial State)	Precision Polishing Service	Standard PCD polishing services deliver Ra < 5 nm, directly meeting the initial conditions of this study. SCD polishing achieves industry-leading Ra < 1 nm.
Gate/Contact Integration	Custom Metalized Wafers	Our internal capabilities support the critical Au ohmic contacts used here, as well as complex stacks (Ti/Pt/Au, W/Pt/Au, etc.) required for various MESFET architectures.

Advanced Customization Potential

The success of the plasma treatment relies on controlling the atomic hydrogen environment and its subsequent etching and passivation effects.

Custom Dimensions: The study utilized 15 mm x 15 mm samples. 6CCVD provides precision laser cutting for any custom dimension or shape required for standard device fabrication, accommodating plates up to 125 mm (PCD).
Metalization Support: The research required low-resistance Au contacts (R_c < 10^-5 Ω·cm²). 6CCVD offers in-house deposition of Au, Ti, Pt, Pd, W, and Cu metal stacks, providing ready-to-use substrates for subsequent Hall measurement or device integration.
Engineering Support: 6CCVD’s in-house PhD team can assist researchers and technical engineers in optimizing material selection and surface preparation protocols (including advanced cleaning/oxidation steps) to replicate or extend the plasma H-termination results achieved here. We provide consultation focused specifically on enhancing carrier density uniformity and stability for H-terminated diamond MESFET projects.
Global Supply Chain Advantage: We offer global shipping (DDU default, DDP available) ensuring high-purity, custom-engineered diamond substrates reach your lab efficiently and reliably, wherever you are.

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

View Original Abstract

The H-terminated diamond films, which exhibit high surface conductivity, have been used in high-frequency and high-power electronic devices. In this paper, the surface conductive channel on specimens from the same diamond film was obtained by hydrogen plasma treatment and by heating under a hydrogen atmosphere, respectively, and the surface carrier transport characteristics of both samples were compared and evaluated. The results show that the carrier mobility and carrier density of the sample treated by hydrogen plasma are 15 cm2·V−1·s−1 and greater than 5 × 1012 cm−2, respectively, and that the carrier mobilities measured at five different areas are similar. Compared to the hydrogen-plasma-treated specimen, the thermally hydrogenated specimen exhibits a lower surface conductivity, a carrier density one order of magnitude lower, and a carrier mobility that varies from 2 to 33 cm2·V−1·s−1. The activated hydrogen atoms restructure the diamond surface, remove the scratches, and passivate the surface states via the etching effect during the hydrogen plasma treatment process, which maintains a higher carrier density and a more stable carrier mobility.

Tech Support

Original Source

DOI: https://doi.org/10.1007/s12613-017-1469-3