Sapphire substrates are ideal for use instead of glass substrates when optical transmission is required in the ultraviolet (above 200 nm) or infrared (below 5 μm) range. Low-temperature optical measurements will also benefit from the higher thermal conductivity of sapphire substrates, and they may also be used in high temperature environments up to 2300 K.
Product Specifications
We offer sapphire substrates with two different surface finish qualities. Our 'Standard' sapphire substrates have been polished to a surface quality of 60/40 scratch-dig, have an RMS roughness of ~0.3 nm, and are suitable for most applications (including spectroscopy or thin-film deposition).
In comparison, our 'Ultra Smooth' sapphire substrates have been polished to a surface quality of 10/5 scratch-dig, have an RMS roughness of ~0.1 nm, and are suitable for applications involving atomic force microscopy, 2D materals, or any application where surface quality is crucial.
Properties | Standard | Ultra Smooth |
| Substrate size | 20 mm x 15 mm | 20 mm x 15 mm |
| Thickness | 1.1 mm | 1.1 mm |
| Material | Synthetic sapphire | Synthetic sapphire |
| Surface finish (scratch-dig) | 60/40 (both sides polished) | 10/5 (both sides polished) |
| Surface roughness (RMS) | ~0.3 nm | ~0.1 nm |
| Surface orientation | C-plane | C-plane |
| Applications | UV/optical/NIR spectroscopy | Atomic force microscopy, 2D material substrate |
Comparison Between Float Glass and Sapphire
Properties | Float Glass | Sapphire |
Hardness (Mohs) | 5.5 | 9 |
Density (g/cm3) | ~2.5 | 3.975 |
Compressive strength (MPa) | 1000 | 2000 |
Transmission window (nm) | ~350-2000 | ~200-5000 |
Refractive index n (k) 300 nm 600 nm 2000 nm 5000 nm |
1.55 (5.0×10-5) 1.52 (4.5×10-7) 1.50 (4.4×10-6) 1.39 (3.0×10-3) |
1.91 (1.7×10-8) 1.76 (2.0×10-8) 1.74 (2.5×10-8) 1.62 (3.1×10-8) |
Thermal conductivity (W/m.K) 30 K 300 K |
0.2 0.9 |
10000 40 |
Melting point (K) | 950 | 2300 |
Specific heat capacity (J/K.kg) | 870 | 750 |
Chemical Properties
Sapphire is a crystalline form of aluminium oxide (Al2O3). It is formed of Al3+ cations and O2- anions arranged in a hexagonal lattice. It is extremely unreactive and chemically-resistant to acids and alkalis, including hydrofluoric acid.
Mechanical Properties
Sapphire is exceptionally hard with a Mohs hardness of 9, second only to diamond (which has a hardness of 10). For comparison, glass has a hardness of ~5.5. This makes it extremely scratch-resistant.
Optical Properties
Sapphire is birefringent, meaning that its refractive index depends on the direction at which the light propagates through the crystal and its polarisation. While birefringence has uses in various optical elements, it is generally undesirable in a substrate used for optical measurements.
To overcome this, our sapphire is cut along the C-plane which eliminates polarisation-dependent birefringence for normally-incident light. Sapphire is transparent to wavelengths of light between 200 nm and 5 µm, making it an excellent choice for UV and near/mid-IR applications. Sapphire has a refractive index of ~1.76 in the visible spectrum.
Below is a comparison of the optical transmission between our sapphire substrates and our quartz-coated glass substrates, showing the superior UV transmission of sapphire. Note: The lower transmission of sapphire in the wavelength range from 350nm - 1000nm is due to its higher real refractive index (n) causing greater reflection of incident light at the air-substrate interface.
Thermal Properties
Sapphire has a high thermal conductivity of ~40 W/m.K at room temperature. This is almost 50 times higher than glass, and twice as high as stainless steel. This value increases to ~10000 W/m.K as temperature is reduced. This makes sapphire highly suitable for low-temperature optical measurements where thermal equilibrium between the sample and cryostat is required. It is also suitable for use in high-temperature environments up to 2300 K. Our sapphire substrates are polished to optical quality, and have an RMS roughness significantly below than that of our glass substrates.
To the best of our knowledge the technical information provided here is accurate. However, Ossila assume no liability for the accuracy of this information. The values provided here are typical at the time of manufacture and may vary over time and from batch to batch.
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Reference material, accompanied by a certificate, one or more of whose property values are certified by a procedure, which established its traceability to an accurate realization of the unit in which the property values are expressed, and for which each certified value is accompanied by an uncertainty at a stated level of confidence. (Brammer StandardBASARMIetc). (ISO Guide 30-1992)
标准品CRM：标准物质/标准品附带析证书属性值某项或若干项都按照某程序进行验证验证程序建立些属性值所表述体系精确体现追溯性每经验证数值都伴随着某特定置信水平确定度（BS,NISTBASARMI等）（ISO Guide 30-1992）
Reference Materials（RM）
Materials or substance one or more of whose property values are sufficiently homogeneous and well established to be used for the calibration of an apparatus, the assessment of a measurement method, or for assigning values to materials. （ISO Guide 30-1992）
照品RM：种原料或物质其某种或几种属性值表现充均性并且用于设备校准析评估或者物质定植（ISO Guide 30-1992）
