FREE shipping to on qualifying orders when you spend or more, processed by Ossila BV. All prices ex. VAT. Qualifying orders ship free worldwide! Fast, secure, and backed by the Ossila guarantee. It looks like you are visiting from , click to shop in or change country. Orders to the EU are processed by our EU subsidiary.

It looks like you are using an unsupported browser. You can still place orders by emailing us on, but you may experience issues browsing our website. Please consider upgrading to a modern browser for better security and an improved browsing experience.

Product Code S2005A1-1
Price £26 ex. VAT

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 three 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.

We also stock sapphire with a 'Coarse' surface finish (although still smoother than most glass substrates) with better than 80/50 scratch-dig and a slightly higher RMS roughness of ~0.7 nm. If you are not concerned about small amounts of optical scatter, these substrates are ideal.

Properties Standard Ultra Smooth Coarse
Substrate size 20 mm x 15 mm 20 mm x 15 mm 20 mm x 15 mm
Thickness 1.1 mm 1.1 mm 1.1 mm
Material Synthetic sapphire Synthetic sapphire Synthetic sapphire
Surface finish (scratch-dig) 60/40 (both sides polished) 10/5 (both sides polished) Better than 80/50 (both sides polished)
Surface roughness (RMS) ~0.3 nm ~0.1 nm ~0.7 nm
Surface orientation C-plane C-plane C-plane
Applications UV/optical/NIR spectroscopy Atomic force microscopy, 2D material substrate UV/optical/NIR spectroscopy
sapphire substrate AFM
Atomic force microscope images of the surface of sapphire substrates. Left: 'Standard' surface finish (scratch-dig 60/40). Center: 'Ultra Smooth' surface finish (scratch-dig 10/5). Right: 'Coarse' surface finish (scratch-dig better than 80/50).

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





Melting point (K) 950 2300
Specific heat capacity (J/ 870 750
sapphire crystal structure planes
The crystal structure of sapphire (left) has numerous symmetry planes (right), along which the properties of the material differ slightly.

Chemical Properties

Sapphire is a crystalline form of aluminum 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.

sapphire optical transmission spectrum
Comparison between the optical transmission of a sapphire substrate (blue line) and a quartz-coated substrate (grey line).

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.

Return to the top