Introduction to Crystal Growth
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-10-11 |
| Journal | International Journal for Research in Applied Science and Engineering Technology |
| Authors | M. Sanjiv |
| Citations | 7 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis document provides a comprehensive engineering review of crystalline materials, focusing on structure, properties, growth methodologies, and technological applications.
- Fundamental Distinction: The review establishes the critical difference between single crystalline, polycrystalline, and amorphous solids based on translational symmetry (long-range vs. local order), which dictates mechanical, optical, and electrical performance.
- Single Crystal Necessity: Single crystals are essential for high-performance applications (e.g., oscillators, optical devices) due to their anisotropy, lack of grain boundaries, and minimal defects, which prevent signal scattering and current obstruction.
- Industrial Growth Techniques: Key industrial methodsâCzochralski (for large-grain semiconductors like Si), Bridgman (for controlled solidification), and various solution/vapor deposition techniquesâare detailed, highlighting their suitability for specific material requirements.
- Quality Control: Standard characterization techniques (XRD, Laue Diffraction, UV/VIS/NIR, FTIR) are outlined as necessary tools for assessing crystal structure, orientation, composition, and purity.
- Advanced Application Case Study: Cadmium Telluride (CdTe) is highlighted as a superior direct conversion semiconductor material for high-energy radiation detectors, offering significantly higher absorption (effective atomic number 50) compared to traditional Si (14) or Ge (32) detectors.
- Driving Force: The artificial growth of crystals is necessary to control orientation, lattice parameters, and purity, enabling the development of materials tailored for multi-billion dollar semiconductor and microelectronic industries.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| CdTe Effective Atomic Number | 50 | N/A | High radiation detection sensitivity |
| Si Atomic Number | 14 | N/A | Comparison material for radiation detection |
| Ge Atomic Number | 32 | N/A | Comparison material for radiation detection |
| UV/VIS/NIR Spectral Range | 175 to 3300 | nm | Optical characterization range |
| FTIR Spectral Range | 4000 to 400 | cm-1 | Infrared spectroscopy range |
| XRD Detection Limit | ~2 | % | Minimum concentration for mixed material identification |
| Laue Diffraction Spot Diameter | 1.5 | mm | Information area size for crystal orientation analysis |
| Cubic Crystal Angles | 90 | degrees | alpha=beta=gamma |
| Hexagonal Crystal Angles | 90, 120 | degrees | alpha=beta=90°, gamma=120° |
| CdTe Absorption (10 mm thickness) | ~100 | % | Absorption rate for 100 keV X-ray detection |
Key Methodologies
Section titled âKey MethodologiesâThe paper reviews four primary categories of crystal growth techniques and four major characterization methods:
Crystal Growth Methods
Section titled âCrystal Growth Methodsâ- Growth From The Solid Phase (SSCG):
- Crystals are grown from a polycrystalline matrix, initiated by single-crystal seeds.
- External pressure is often applied to reduce porosity in the final single crystal.
- Growth From The Melt:
- Involves melting the charge and cooling the liquid below its freezing point for resolidification.
- Czochralski Process: Pulling a rotating seed crystal slowly from the melt surface to produce large, uniform, cylindrical single crystals (e.g., silicon).
- Bridgman Method: Lowering a crucible (often with a conical tip for single nucleation) through a temperature gradient in a vertical furnace, allowing the melt-solid interface to move slowly.
- Growth From The Liquid Solution:
- Crystallization occurs from a critically supersaturated solution.
- Flux Growth: Uses a solvent (flux) to dissolve components at high temperatures, suitable for growing crystals free from thermal strain and often displaying natural facets.
- Growth From The Vapour Phase:
- Chemical Vapour Deposition (CVD): Deposition of a solid on a heated surface from a chemical reaction in the vapor phase.
- Physical Vapour Deposition (PVD): Transferring material from a solid source onto a substrate via vaporization (e.g., sputtering, evaporation).
Characterization Techniques
Section titled âCharacterization Techniquesâ- X-Ray Powder Diffraction (XRD):
- Used for rapid phase identification of crystalline materials and determination of unit cell dimensions.
- Based on constructive interference satisfying Braggâs Law.
- Laue Diffraction Method:
- Primarily used to determine the orientation and perfection of large single crystals.
- Analyzes the regular array of spots produced by X-rays scattered by atomic planes.
- UV/VIS/NIR Spectroscopy:
- Determines optical properties (transmittance, reflectance, absorbance) of crystal samples.
- Operates in the optical range between 175 nm and 3300 nm.
- FTIR Spectroscopy (Fourier Transform Infrared):
- Obtains the infrared spectrum of absorption/emission for structural analysis and quantification of inorganic and organic compounds.
- Uses an interferometer and Fourier transformation to decode the signal.
Commercial Applications
Section titled âCommercial ApplicationsâThe use of single crystals is critical across numerous high-technology sectors, driven by the need for precise, defect-free materials.
| Material Class | Example Devices | Key Crystals Used |
|---|---|---|
| Semiconductors | Integrated circuits, Transistors, Electrical diodes, Radiation detectors | Si, Ge, GaAs, InSb, CdTe, GaN |
| Optical Materials | Laser hosts, Electro-optic devices, Lenses, Prisms, Windows | YAG, Ruby (Al2O3:Cr3+), LiNbO3, Quartz |
| Piezoelectric Materials | Resonant bulk wave devices, Transducers (e.g., sensors) | SiO2, LiTaO3, LiNbO3, ADP |
| Magnetic Materials | Microwave filters, Tape heads | Garnets (Y3Fe5O12), Ferrites |
| Pyroelectric Materials | Fire alarms, Thermal sensors | TGS, LiTaO3, BaxSrx-1Nb2O6 |
| High-Resolution Imaging | Direct conversion radiation detectors, Medical gamma-ray imaging | Cadmium Telluride (CdTe), Cadmium Zinc Telluride (CdZnTe) |
| Frequency Control | Quartz oscillators | Single-crystal quartz (for superior frequency stability) |
View Original Abstract
The crystal, with its regular atomic construction, is the most commonly encountered state of solid materials.In the earthâs surface, crystals were grown by extreme conditions of high temperature, pressure and other environmental factors.To be specific each crystal starts small and grows as more atoms are added.Many grow from water rich in dissolved minerals, but they can also be grown from melted rock and even vapor.Under the influence of different temperatures and pressures, atoms combine in an amazing array of crystal shapes.The process can take as little as a few days to maybe a thousand years.Crystals that are found in Earthâs crust are often formed in this manner.These crystals were formed over a million years ago inside the Earthâs crust.They occurred when the liquid in the Earth consolidates.Crystals are not new to mankind, as they exist in the ancient period.Salt crystals were used in many cultures for food and other purposes.These salt crystals were grown by evaporating seawater in direct sun.In some cultures, pure salt crystals were used as currency and for trading as it was viewed as a precious resource.Some even waged wars against the salt accusation.The Ancient Egyptians used lapis lazuli, turquoise, carnelian, emerald, and clear quartz in their jewelry.They used some stones for protection and health, and some crystals for cosmetic purposes, like galena and/or malachite as eye shadow.Every part of the world considers Diamond, sapphire, and Ruby as a valuable resources.In India, the Mughals and other kingdoms used Diamond and Sapphire for exquisite ornaments and necklaces.This was the reason India was constantly colonized by the Mughals and by the British.India is the first country to open mines to produce diamonds.Probably the first reference to crystals in Ancient Rome was reported by Pliny the Elder (I Century AD) in his âNatural Historyâ, where he describes windows and greenhouses of the richer inhabitants of the Roman Empire being covered by crystals of âLapis specularisâ, the Latin name for large transparent crystals of gypsum.This dehydrated form of calcium sulfate was extracted by Romans in SegĂłbriga (Spain) because of its crystal clarity, size (up to one meter), and perfect flatness.The German mathematician, astronomer, and astrologer Johannes Kepler (1571-1630) marveled when a snowflake landed on his coat showing its perfect six-cornered symmetry.In 1611 Kepler wroteâ Six-cornered Snowflakeâ (Latin titleâ Strena Seu de Nive Sexangulaâ) the first mathematical description of crystals. II.CRYSTALS IN MODERN ERA.We cannot think of a modern technology that would be half as good without the use of crystals.Crystals are the unacknowledged pillars of modern technology.Without crystals, there would be no electronic industry, no photonic industry, and no fiber-optic communications, which depend on materials/crystals in the field of semiconductors, superconductors, polarizers, transducers, radiation detectors, ultrasonic amplifiers, ferrites, magnetic garnets, solid-state lasers, non-linear optics, piezoelectric, electro-optic, acoustic-optic, photosensitive, refractory of different grades, crystalline films for microelectronics and computer industries.The list is almost endless.In the past few decades, there has been a growing interest in crystal growth, particularly given the increasing demand for materials for technological applications.Quartz crystals are one of the common components in devices like cell phones, television receivers, and, of course, watch and clocks.One of the main reasons quartz is used in so many electronic devices is because of its piezoelectric property.Garnet crystals are used to make sandpaper.Corundum crystals are used to make grinding wheels and durable sandpaper.Diamond crystals are used in rock-cutting drill bits and saws.Calcite crystals are ground up and used to make Tums and heated to make cement.Gypsum crystals are heated and powdered to make plaster.Halite (salt) crystals are used on food and in many industrial chemical processes.Magnetite and hematite crystals are iron ore.Ruby crystals were used in the earliest red lasers.Even in this modern civilized world ornaments such as Rings, necklaces, bracelets, and other cosmetic jewelry made from Diamond, Sapphire, and Ruby are crazed over and still regarded as a prized possession.But the slight twist is that now these crystals can be manmade and can be grown in Labs.