OBSERVATION OF PHASE TRANSITIONS FEATURES IN SILICON AT HIGH LOCAL PRES-SURE UNDER INDENTATION

At a Glance

Metadata	Details
Publication Date	2015-03-16
Journal	Izvestiya Vysshikh Uchebnykh Zavedenii Materialy Elektronnoi Tekhniki = Materials of Electronics Engineering
Authors	С. В. Прокудин, А. С. Усеинов
Analysis	Full AI Review Included

Technical Documentation & Analysis: Diamond Indenters for Electro-Mechanical Phase Transition Studies

This documentation analyzes the research paper “Observation of Phase Transitions in Silicon under High Local Pressure during Indentation,” focusing on the application of Boron-Doped Single Crystal Diamond (BDD SCD) indenters for simultaneous mechanical and electrical characterization.

Executive Summary

This study successfully utilized a Boron-Doped Single Crystal Diamond (BDD SCD) indenter to perform simultaneous nanoindentation and electrical current measurement, providing critical insights into high-pressure phase transitions in silicon (Si).

Core Achievement: Validation of BDD SCD as a superior indenter material for combined electro-mechanical analysis, enabling the detection of structural phase changes (e.g., Si-I to metallic Si-II) via both load-displacement curves and current jumps.
Material Specification: The indenter was fabricated from BDD SCD with a high doping concentration (10¹⁹ cm^-3) and low resistivity (0.1 Ω·cm), essential for accurate current sensing.
Critical Event Detection: The methodology precisely identified the moment of silicon oxide (SiO₂) layer puncture (~5 nm depth) and correlated current discontinuities with the “pop-in” (Si-I → Si-II) and “pop-out” (Si-II → Si-III/Si-XII/a-Si) events.
Phase Confirmation: Raman spectroscopy confirmed the formation and localization of metastable high-pressure phases (Si-III, Si-XII, and amorphous a-Si) within a < 2 µm radius of the indentation center.
Application Relevance: The findings are highly relevant for optimizing mechanical processing (cutting, grinding) of semiconductors and understanding wear, friction, and erosion mechanisms in electronic materials.

Technical Specifications

The following hard data points were extracted from the experimental section of the research paper:

Parameter	Value	Unit	Context
Indenter Material	Boron-Doped SCD	N/A	Berkovich pyramid shape
Indenter Dopant Concentration	10¹⁹	cm^-3	Required for semiconductor properties
Indenter Resistivity	0.1	Ω·cm	Electrical property of BDD indenter
Effective Indenter Tip Size	~1.3	µm	Size of the Berkovich tip
Applied Load Range (P_max)	1 - 100	mN	Nanoindentation test range
Loading Speed	5	nm/sec	Rate of indenter displacement
Applied Voltage (V)	+3	V	For electrical current measurement
Critical Pressure (Si-I > Si-II)	~12	GPa	Pressure required for phase transition
Critical Load (Si-I > Si-II)	~5	mN	Load corresponding to “pop-in” event
SiO₂ Puncture Depth	~5	nm	Initial penetration depth where current sharply increases
Volume Change (Si-I > Si-II)	2.73	cm³/mol	Associated with structural transformation
Metastable Phase Localization	< 2	µm	Distance from indentation center confirmed by Raman

Key Methodologies

The experiment combined advanced nanoindentation techniques with simultaneous electrical and spectroscopic analysis to characterize localized phase transitions in silicon.

Sample Selection: Boron-doped single-crystal silicon samples (KDB(100)-7.5 and KDB(111)-0.1) were used to study the influence of crystal orientation and doping level on phase transition behavior.
Indenter Fabrication: A Berkovich pyramid indenter was fabricated from Boron-Doped Single Crystal Diamond (BDD SCD), ensuring the necessary electrical conductivity for current measurement.
Instrumented Nanoindentation: Load (P) versus displacement (h) curves were recorded using a “NanoScan-3D” system, adhering to the international standard ISO 14577.
Simultaneous Electro-Mechanical Testing: A constant voltage (+3 V) was applied between the BDD indenter and the silicon sample. The resulting current flow through the contact area was recorded concurrently with the mechanical P(h) curve.
Loading Cycle: The indenter was loaded up to 100 mN at a controlled rate of 5 nm/sec, held for 5 seconds, and then unloaded, allowing observation of both forward (Si-I → Si-II) and reverse (Si-II → Si-III/Si-XII/a-Si) phase transitions.
Post-Indentation Analysis: Raman spectroscopy was employed on the indented areas to confirm the presence of high-pressure metastable phases (Si-III, Si-XII, and a-Si) and map their spatial localization.

6CCVD Solutions & Capabilities

The successful execution of this research hinges on the availability of high-quality, electrically conductive diamond material for the indenter tip. 6CCVD is uniquely positioned to supply and customize the required materials for replicating or extending this advanced electro-mechanical research.

Applicable Materials

To replicate the simultaneous mechanical and electrical measurements described in this paper, researchers require highly conductive diamond.

Material of Choice: Heavy Boron-Doped Single Crystal Diamond (BDD SCD).
- 6CCVD Specification: We provide BDD SCD plates with precise, controllable doping levels (e.g., 10¹⁹ cm^-3 or higher) and low resistivity (down to 0.1 Ω·cm), matching the electrical performance required for current sensing during nanoindentation.
Alternative: Heavy Boron-Doped Polycrystalline Diamond (BDD PCD).
- For applications requiring larger contact areas or substrates up to 125 mm, BDD PCD offers excellent conductivity and mechanical robustness.

Customization Potential

The experiment utilized a specific Berkovich geometry and required ultra-smooth surfaces for reliable contact. 6CCVD offers comprehensive customization services to meet these stringent demands:

Requirement from Paper	6CCVD Capability	Technical Advantage
BDD Indenter Material	SCD plates up to 500 µm thick	Guaranteed doping consistency and orientation control
Precision Tip Geometry	Custom laser cutting and shaping services	Preparation of BDD blanks for Berkovich or other indenter geometries
Surface Quality (SCD)	Polishing to Ra < 1 nm	Essential for minimizing contact resistance and ensuring accurate mechanical response
Electrical Contacts	Custom Metalization (Au, Ti, Pt, W)	In-house capability to deposit robust electrical contacts directly onto the BDD material for reliable wiring
Large-Scale Testing	PCD Wafers up to 125 mm	Enables scaling up high-pressure studies or developing large-area diamond sensors

Engineering Support

The complexity of correlating mechanical deformation, electrical current, and phase transitions demands expert material knowledge.

Application Expertise: 6CCVD’s in-house PhD team specializes in the physical and electrical properties of CVD diamond. We can assist researchers in selecting the optimal BDD doping concentration and crystal orientation (<100> or <111>) required for similar Electro-Mechanical Phase Transition projects.
Global Logistics: We ensure reliable global shipping (DDU default, DDP available) of sensitive diamond materials, supporting international research efforts without logistical delays.

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

View Original Abstract

Instrumented indentation is a very promising technique for studying structural phase transitions in crystalline materials such as silicon.In the present work silicon samples with different crystallographic orientations and doping rates were investigated using indentation with a pyramid indentor of Berkovich type. For studying the electrical properties the indentor was made of semiconductor boron−doped single crystalline diamond. For verification of structural transitions in silicon Raman spectroscopy technique was applied.Electrical current through the contact area under the indentor was measured simultaneously with recording the mechanical response of the material during the indentation process. It is shown that variation in current value gives additional information about the conditions of contact between the indentor and the sample surface. The influence of variations in resistivity and contact area on the measured electrical current value is discussed.

Tech Support

Original Source

DOI: https://doi.org/10.17073/1609-3577-2012-1-17-21