Polycrystalline Germanium N Type Crystal:75mm Dia. x 3.0mm Thick, Uncoated, Ge Window

$467.70

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Additional information

Weight	0.5 kg
Dimensions	12 × 10 × 8 cm

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General Specification

Material: Optical-Grade Monocrystalline Germanium ( resistivity of 5-40 ohm cm)
Diameter: Ranges from 12mm to 380mm
Length: Customizable
Electrical Resistivity: From 0.005Ω to 50Ω/cm
Crystal Purity: Between 99.999% and 99.9999%
Surface Roughness: From Ramax 0.2μm to 4.0μm
Refractive Index at 10.6μm: 4.0052
Absorbance at 10.6μm: ≤0.035
Thickness Tolerance: ± 0.10mm
Diameter Tolerance: +0.00/-0.05mm
Edge Finish: Finely ground
Surface Quality: 60/40 Scratch/Dig
Surface Flatness: ≤ 5 Fringes at 633nm
Parallelism: ≤ 3 Arc minutes
Orientation: <111>
Transmission Range: Covers IR wavelengths from 3 to 14 microns
Coating Specification: Upon Request, Anti-Reflective/Diamond-Like Carbon (AR/DLC)
Coating: AR coated from 3-14 microns, or DLC (Diamond-Like Carbon) in black/dark grey colour, with average transparency (Tavg) greater than 80%
Double-sided Anti-Reflective coating with an average transparency (Tavg) greater than 85%

Here is the clearer plot of the typical transmission curve for a 1mm thick Germanium (mono-crystalline) window. The graph shows a sharp increase to 50% transmission starting from 2 µm and remains constant through 16 µm. This graph provides a visual representation of how the transmission behaves across the specified wavelength range.

Physical Properties

This table details various physical properties of the material, which could include mechanical, thermal, and electrical characteristics, relevant for applications that require precise material specifications.

Optical Properties

This table provides the refractive index of a material over the wavelength range from 2 micrometres to 14 micrometres, useful for applications requiring optical properties data at different IR spectrums.

About DLC Coating

Shape Optics Diamond-Like Carbon (DLC) Coated Germanium Windows are crafted for robustness and longevity. These windows are equipped with a high-efficiency broadband anti-reflection coating on one side and a durable DLC coating on the opposite side, ensuring outstanding transmission and resistance to environmental conditions. The DLC-coated surface is engineered to endure extreme temperature fluctuations ranging from -80 to +160°F, continuous exposure to salt spray for 24 hours, salt solubility during a 24-hour immersion, and up to 5,000 wiper oscillations with a sand and slurry mixture. Moreover, ShapeOptics DLC Coated Germanium Windows comply with the MIL-C-675C standards for severe abrasion resistance.

About AR Coating

Shape Optics offers Germanium (Ge) Windows with three options for anti-reflection coatings to cater to different infrared (IR) applications: a 3 – 5μm coating for mid-infrared use, a 3 – 12μm coating for broadband multispectral applications, and an 8 – 12μm coating for thermal imaging systems. Given germanium’s high index of refraction, approximately 4.0 across the 2 – 14μm wavelength range, applying an anti-reflection coating is crucial for achieving adequate transmission within the desired spectral region.

Germanium is prone to thermal runaway, a condition where its transmission efficiency declines as temperatures rise. Therefore, it is recommended to operate Shape Optics Germanium Windows at temperatures below 100°C to maintain optimal performance. Additionally, with a high density of 5.33 g/cm³, germanium windows should be carefully integrated into designs where weight sensitivity is a factor.

The material’s Knoop Hardness, at 780, is roughly double that of magnesium fluoride, making germanium windows exceptionally suitable for demanding IR applications where durable optics are essential.

About Coating Quality

Adhesion Test Compliant with MIL-C-675C military standards, an adhesion test involved applying a tape that meets LT-90 specifications onto the lens film layer. The tape was affixed fully and then removed vertically. This procedure was performed three times, resulting in no blistering or peeling.
Temperature Test In line with MIL-C-675C specifications, test pieces were subjected to temperatures of -62±1℃ and 71±1℃. After maintaining them at room temperature (16℃~32℃) for two hours, the adhesion test was repeated, confirming no film detachment.
Abrasion Resistance Test Conforming to MIL-C-675C and CCC-C-440 standards, the abrasion resistance test involved a gauze tester applying a minimum force of 1.0 lbs (0.45 kg) to the film. This was repeated 25 times with gauze widths of 1/4 inch (6.4mm) and 3/8 inch (9.5mm), ensuring no damage occurred to the film surface.
Humidity Test Under MIL-C-675C criteria, the test piece was placed in a controlled temperature and humidity chamber set to 49 ±2℃ and 95%~100% humidity for 24 hours. The film remained intact, with no peeling, scratches, or other defects.
Solvent and Cleaning Testing Following MIL-C-675C specifications, test pieces were exposed to room temperature conditions (16℃~32℃) and tested with acetone and alcohol for at least 10 minutes each. After air drying and subsequent cleaning with a cotton cloth soaked in alcohol, the film surface showed no signs of peeling or scratches.
Salt Spray Test After 100 hours in a 35°C environment with a 5% saltwater concentration, the film showed no signs of damage.

Monocrystalline vs. Polycrystalline Germanium

Polycrystalline Germanium:

Structure: Made up of many small crystalline grains or crystals, each with a different orientation.
Production: Easier and cheaper to produce compared to monocrystalline germanium.
Efficiency: Generally less efficient in electronic and photovoltaic applications because grain boundaries can scatter charge carriers, reducing their mobility.
Applications: Often used in less demanding electronic applications, such as infrared optics, and in some solar cells.

Monocrystalline Germanium:

Structure: Consists of a single, continuous crystal lattice with no grain boundaries.
Production: More difficult and expensive to produce as it requires precise control of the crystal growth process.
Efficiency: Higher efficiency in electronic and photovoltaic applications due to fewer defects and better charge carrier mobility.
Applications: Preferred for high-performance applications, such as in high-speed transistors, and high-efficiency solar cells.

N-Type vs. P-Type Germanium

N-type Germanium:

Doping: Doped with elements that have more valence electrons than germanium (group V elements like phosphorus, arsenic, or antimony).
Charge Carriers: The majority charge carriers are electrons.
Behavior: When an electric field is applied, electrons move towards the positive terminal, making it a negative type (N-type) semiconductor.
Applications: Used in various electronic components, including diodes, transistors, and integrated circuits.

P-type Germanium:

Doping: Doped with elements that have fewer valence electrons than germanium (group III elements like boron, gallium, or indium).
Charge Carriers: The majority charge carriers are holes (the absence of an electron).
Behavior: When an electric field is applied, holes move towards the negative terminal, making it a positive type (P-type) semiconductor.
Applications: Also used in electronic components, often in conjunction with N-type materials to create P-N junctions, which are essential for diodes, transistors, and solar cells.

Comparison of P-type and N-type Semiconductors:

Feature	P-type	N-type
Dopant Elements	Boron, Gallium, Indium	Phosphorus, Arsenic, Antimony
Majority Charge Carriers	Holes	Electrons
Direction of Current Flow	Holes move to negative terminal	Electrons move to positive terminal