EP4466387A1

EP4466387A1 - Method of depositing a coating layer

Info

Publication number: EP4466387A1
Application number: EP23701600.1A
Authority: EP
Inventors: Philip Savage
Original assignee: Pilkington Group Ltd
Current assignee: Pilkington Group Ltd
Priority date: 2022-01-20
Filing date: 2023-01-13
Publication date: 2024-11-27
Also published as: GB202200721D0; WO2023139347A1

Abstract

The invention relates to a method of depositing a coating layer comprising a step of sputtering a target comprising silicon, aluminium and samarium under an atmosphere comprising a noble gas, oxygen and nitrogen to form the coating layer on the first surface of a substrate, wherein the atmosphere comprises a percentage of nitrogen based on nitrogen and oxygen of from 1 to 90% by volume such that a more controllable and repeatable deposition may take place, also provided are a substrate coated with such a coating layer, laminated structures comprising such substrates, and glazing panes comprising such substrates and laminated structures.

Description

Method of depositing a coating layer

The invention aims to provide a method of depositing a coating layer on a substrate. More particularly, the invention aims to provide a method of depositing a coating layer comprising a step of sputtering a target comprising silicon, aluminium and samarium. The invention also relates to a substrate comprising such a coating layer, laminated structures comprising such substrates, and glazing panes comprising such substrates or laminated structures.

It is well known that films comprising samarium may absorb UV light and then emit visible light. Such films may be incorporated in devices for converting solar radiation, as disclosed in, for example, US 20210280727 Al.

In addition, the deposition of samarium containing coatings is known, for example de Vries et al in the Journal of Luminescence Volume 225, September 2020, 117321 disclose a method of combinatorial reactive co-sputtering using Al, Si and Sm targets in an Ar + 02 atmosphere, and Futagami et al in the Journal of the Ceramic Society of Japan, 107.1248 (1999): 707-710 disclose samarium -doped aluminosilicate coatings prepared by rf magnetron sputtering in both pure argon and in a mixture of argon and hydrogen at the substrate temperatures of 25, 200 and 300°C. Such films may be employed as luminescent films.

However, it is desirable to improve the luminescence properties of coating layers comprising samarium, and to provide a method that allows the production of coating layers comprising samarium with high luminescence in a repeatable manner.

Therefore, there is provided according to a first aspect of the present invention a method of depositing a coating layer on a substrate comprising the steps of: providing a substrate with a first surface and a second surface; providing a target comprising silicon, aluminium and samarium; and sputtering the target comprising silicon, aluminium and samarium under an atmosphere comprising a noble gas, oxygen and nitrogen to form the coating layer on the first surface of the substrate, wherein the atmosphere comprises a percentage of nitrogen based on nitrogen and oxygen of from 1 to 90% by volume. When applying coatings comprising silicon, aluminium and samarium the inventors discovered that a layer that is substoichiometric in oxygen is desirable in order to produce luminescence, but if there is too little oxygen in the layer the absorption of the coating is increased, which is unsuitable for many applications, for example those where the film should be substantially transparent. In addition, a particularly low oxygen content may have a reduced the quantum yield of luminescence.

A method of influencing the oxygen content of a sputtered coating is to control the oxygen proportion in the sputtering atmosphere. When sputtering a coating from a target without a significant oxygen content in an atmosphere comprising oxygen (so called reactive sputtering), oxygen is incorporated from the sputtering atmosphere into the coating. The amount of oxygen that is incorporated into the coating may be varied by varying the oxygen proportion of the sputtering atmosphere. The proportions of atmosphere gas components are typically varied by varying the flow rate of the individual components into the sputtering chamber or premixing chamber, and the skilled person understands that the flow rate proportions are a suitable proxy for the sputtering atmosphere. Therefore, it is desirable to provide a sputter atmosphere of a particular oxygen proportion, using particular flow rates of gases, in order to control the amount of oxygen in the coating, and therefore its luminescent and visible absorption properties.

However, sputtering processes include hysteresis mechanisms which influence the composition of the coating layer, such as that depicted in figure 1, wherein the x-axis depicts increasing atmospheric proportion of oxygen Oat and the y-axis depicts increasing proportion of oxygen Onim in the resultant coating layer.

An oxygen atmosphere against oxygen content hysteresis curves may be split into zones: Zone A, where O_at is below a first critical amount Cl where Onim is negligible; Zone B, arrived at by increasing O_at above Cl, wherein Onim is low and the rate of change is low; Zone C, arrived at by increasing O_at above an amount P2, wherein Onim significantly increases with a high rate of change; Zone D, arrived at by increasing O_at further beyond a second critical amount C2, wherein Ofiim is high, either stoichiometric or super-stoichiometric, and the rate of change is low; Zone E, arrived at by decreasing O_at after the second critical amount C2 has been breached, wherein Ofn_m remains high with a low rate of change; and Zone F, arrived at by further decreasing O_at beyond an amount P2, wherein Ofn_m significantly reduces with a high rate of change. Zone C may be considered to be an unstable area, where the rate of change is high, and there is a risk of passing critical amount C2 - once the oxygen proportion is increased beyond the critical amount the system enters Zone D, and a reduction in oxygen proportion does not cause the system to regain the Zone C, but rather Zone E.

The inventors have surprisingly discovered that the hysteresis curve of a coating layer produced by sputtering a target comprising silicon, aluminium and samarium in an atmosphere comprising oxygen is particularly steep. The hysteresis curve of the deposition from a target comprising oxygen is such that in order to provide coatings with desirable oxygen contents concerning luminescence and visible absorption a sputtering atmosphere oxygen proportion is required which is in the unstable area of the hysteresis curve, termed Zone C. This can lead to processing difficulties, wherein routine small variations in the sputter atmosphere oxygen proportion may cause large variations in the oxygen content of the resultant coating layer, leading to coating layers which do not luminesce.

In some cases, the routine variation in the sputter atmosphere oxygen proportion may cause the system to pass from Zone C to Zone D, which may require that the system is reset to Zone A before continuing with deposition. Such a reset causes both lost time and increases wastage, therefore reducing the efficiency of the deposition process.

Crucially, the inventors have learned that the addition of nitrogen to the sputtering atmosphere improves the deposition of a samarium containing layer. In particular, addition of nitrogen allows the hysteresis curve to be altered, such that a more controllable and repeatable deposition may take place. This leads to a more efficient deposition process. The inventors discovered that only relatively small proportions of nitrogen are required.

Therefore, preferably the atmosphere comprises a percentage of nitrogen based on nitrogen and oxygen of from 5 to 70%, preferably of from 10 to 50%, more preferably of from 12 to 30%, by volume.

However, the inventors have further learned that the addition of nitrogen to the sputtering atmosphere increases the inclusion of nitrogen in the resultant coating, and that an increased nitrogen content is associated with a decrease in luminescence. Therefore, it is preferable that sufficient nitrogen is included in the sputtering atmosphere to stabilise the system, and thereby repeatably produce samarium containing coatings with the desired optical and luminescent properties, but the amount of nitrogen in the sputtering atmosphere is minimised, to prevent decreased luminescence in the result coating. As such, preferably the percentage of nitrogen based on nitrogen and oxygen is from 10 to 30 % by volume, preferably from 12 to 25% by volume. A greater flow rate is associated with a decrease in luminescence of the resultant coating, while a lower flow rate is associated with lower repeatability and therefore increased wastage.

Preferably, the target comprises from 80 to 95 wt% silicon, from 1 to 20 wt% aluminium, and from 2 to 10 wt% samarium, preferably wherein the target comprises from 85 to 90 wt% silicon, from 5 to 10 wt% aluminium, and from 3 to 5 wt% samarium.

Preferably, the noble gas is argon.

Preferably, the substrate comprises glass, preferably glass of thickness from 3 to 15 mm, preferably 4 to 12 mm, more preferably 5 to 10 mm, most preferably glass of thickness from 7 to 9 mm.

Preferably, the method further comprises a step of heating the substrate at a temperature in excess of 600 °C after the step comprising sputtering, preferably for at least 3 minutes, more preferably for at least 5 minutes. The inventors have discovered that a heat treatment step of this kind improves the luminescent performance.

In some embodiments, the method further comprises a step of depositing an underlayer prior to the step of sputtering the target comprising silicon, aluminium and samarium, preferably wherein the step of depositing an underlayer layer comprises sputtering a target comprising silicon. Such an underlayer may improve the adhesion of the luminescent coating layer to the substrate and thereby improve the durability of the coating.

Preferably, the step of sputtering comprises voltage controlled deposition. Voltage controlled deposition allows for a particular point on the hysteresis curve to be targeted. A control system will attempt to hold a selected voltage and will react to changes in the sputtering plasma by increasing or decreasing the O2 flow automatically. If the voltage is drifting downwards the O2 flow will be reduced to readjust and the opposite if the voltage is drifting upwards. This keeps the plasma and thus the composition of the deposited material more stable than the selection of a static O2 flow using a flow controller. Voltage controlled deposition is especially required for the long runs needed to deposit the thick layers which are preferable for luminescent coatings. Furthermore, voltage controlled deposition keeps the plasma more stable during the transitions when the carrier moves out from underneath the target at the end of each pass.

According to a second aspect of the present invention, there is provided a substrate comprising a first surface, the first surface comprising a coating layer, and the coating layer comprising silicon, aluminium, samarium, oxygen and nitrogen, wherein the coating layer comprises an atomic percentage of silicon o, an atomic percentage of aluminium 3, an atomic percentage of samarium £, an atomic percentage of oxygen x, and an atomic percentage of nitrogen y, wherein x > y.

Preferably the coating layer is an amorphous or crystalline coating layer, preferably produced via sputtering. Preferably the coating layer is homogenous in samarium. A coating layer that is homogenous in samarium is where the samarium atoms are dispersed evenly through the layer, rather than being incorporated in clumps, particles or other bodies.

Preferably, the surface comprises the coating layer in that the coating layer is adhered directly or indirectly to the surface.

Preferably, the atomic percentage of nitrogen y is from 0.1 to 15, preferably y is from 1 to 10, more preferably y is from 2 to 5.

Preferably, the coating layer comprises samarium with an oxidation state of 2+, and an atomic percentage of samarium with an oxidation state of 2+ is greater than or equal to an atomic percentage of samarium with an oxidation state of 3+. The oxidation states of samarium coating components may be assessed, for example, via XPS.

Preferably, o is from 25 to 40, 3 is from 1 to 5, £ is from 0.01 to 5, and x is from 40 to 70, more preferably o is from 30 to 35, 3 is from 2 to 4, £ is from 0.1 to 0.5, and x is from 50 to 60.

Preferably, the coating layer is substoichiometric in oxygen.

Preferably, the coating layer has a thickness of from 500 to 5000 nm, preferably from 1000 to 2500 nm, more preferably from 1250 to 2250 nm. Such thicknesses are chosen considering the desire for luminescent coatings to be produced efficiently. However, even thicker or even thinner coatings may be used where required by the particular application. Preferably, the substrate comprises glass, preferably glass of thickness from 3 to 15 mm, more preferably 4 to 12 mm, yet more preferably 5 to 10 mm, most preferably glass of thickness from 7 to 9 mm.

The coating layer comprising silicon, aluminium, samarium, oxygen and nitrogen may be the only coating layer on the substrate. However, in some embodiments there may be underlayers and or overlayers provided. Preferred underlayers include oxides and/or nitrides, such as silicon and/or aluminium oxides, silicon and/or aluminium nitrides, silicon and/or aluminium oxynitrides. In some embodiments overlayers may be provided for increased durability.

In some embodiments, over and/or underlayers may include transparent conductive layers, such as those comprising fluorine doped tin oxide.

The substrate may comprise only one coating layer comprising silicon, aluminium, samarium, oxygen and nitrogen. However, the substrate may comprise more than one coating layer comprising silicon, aluminium, samarium, oxygen and nitrogen, preferably separated by additional intermediate layers. Intermediate layers may include, for example, oxides and/or nitrides such as silicon and/or aluminium oxides, silicon and/or aluminium nitrides, silicon and/or aluminium oxynitrides.

According to a third aspect of the present invention, there is provided a laminated structure comprising a substrate comprising a coating layer deposited according to the first aspect, or a substrate according to the second aspect of the invention, adhered to a sheet of material by an adhesive layer; preferably the adhesive layer comprises polyvinyl butyral (PVB).

It is preferable that an adhesive layer is selected which has a high UV transmission, to increase the number of photons in the UV range that reach the luminescent coating. Preferably, a high UV transmission PVB adhesive layer is selected, preferably a PVB adhesive layer wherein the transmission of 350 nm light is greater than 50%, preferably greater than 75%. An example PVB adhesive layer with high UV transmission is TROSIFOL UV+, available from Kuraray Europe GmbH, Germany.

Preferably, the first surface comprising the coating layer is adjacent to the adhesive layer. Preferably, the sheet of material comprises glass, preferably both the substrate and the further sheet of material comprises glass.

According to a fourth aspect of the present invention there is provided a glazing pane comprising a substrate comprising a coating layer deposited according to the first aspect, or a substrate according to the second aspect, or a laminated structure according to the third aspect of the invention.

Preferably the glazing pane is suitable for use in a glazing unit, such as an insulating glazing unit.

The skilled person will appreciate upon consultation of the present specification that optional features of aspects 1, 2, 3, and 4 may be combined with one another without limitation as required.

The invention will now be described with reference to experimental examples and figures, in which:

Figure 1 depicts a typical hysteresis curve indicating the dependence of oxygen content of the resultant coating upon the oxygen content of the sputtering atmosphere;

Figure 2 depicts a measured hysteresis curve indicating the effect of oxygen flow in the sputtering atmosphere upon the measured sputtering voltage in the absence of nitrogen;

Figure 3 depicts the effect of oxygen flow in the sputtering atmosphere upon measured sputtering voltage with changing nitrogen flow;

Figure 4 depicts the apparatus for measurement of luminescence of coatings; and

Figure 5 depicts the dependence of measured photoluminescence emission and visible light absorption upon the nitrogen content of the sputtering atmosphere.

The inventors produced comparative examples and examples according to the invention by the following method. Clear float glass substrates of 6 mm thickness - Pilkington Optiwhite™ available from NSG, UK - were prepared by washing and then submitted to a sputtering process to provide a coating layer on the air side of the float glass from a target comprising SiAISm (Si 89.35wt% I Sm 3.14wt% / Al 7.51wt%). Sputtering was carried out in a pilot-scale Von Ardenne coater using a standard dual magnetron target with a MFG power supply (Huttinger Tig 50) and a power of 15 kW. The argon flow was 250 seem in all experiments, and the oxygen flows varied. Nitrogen flows were varied for examples according to the invention, with zero nitrogen flow for comparative examples. The proportions of gases in the sputtering atmosphere is conventionally controlled by the flow rates of the input gases. The substrate was passed under the target at a speed of 600 mm/min.

A series of comparative examples were prepared according to the method with a proportion of oxygen based on total gas flows 02% as depicted in Table 1, then assessed for luminescence by eye by illuminating with a torch with a UV (365 nm) led bulb. When preparing the comparative examples no nitrogen was introduced into the sputtering atmosphere.

Table 1

As shown by the comparative examples, when layers are produced without nitrogen in the sputtering atmosphere luminescent coatings are not produced consistently i.e. only 3 out of 8 attempts. It was not possible to repeatably produce luminescent coatings even when the same input parameters are used. This indicates that luminescent coatings are produced in the unstable area (C of Figure 1), while non-luminescent coatings are produced in the stable area (D of Figure 1)

A series of depositions was carried out to produce a hysteresis curve for the effect of oxygen flow rate upon sputtering voltage in the absence of nitrogen, as depicted in Figure 2. The measured sputtering voltage is understood by the person skilled in the art to be an indication of the sputtering mode - a high sputtering voltage indicates metallic deposition while a low sputtering voltage indicates oxidised deposition. As such, the measured sputtering voltage curve may be considered to be the inverse of the expected oxygen content of the resultant coating which is depicted in Figure 1. The measured hysteresis curve depicted in Figure 2 is extremely steep: the change between metallic deposition at high voltage deposition and oxidised deposition at low voltage occurs over less than 10 seem. Gas flow controllers may be set at a given flow rate, but the actual flow rate may fluctuate around this value by a whole seem or more, which in this experimental procedure lead to the system falling into a more stable mode which does not produce luminescent coatings, as found in the comparative examples of Table 1.

Therefore, the inventors set out to provide a repeatable method of producing luminescent coatings.

It was theorised that the observed behaviour is due to the desired composition being deposited in an unstable position in the hysteresis curve, which means that small variations in the oxygen atmosphere proportion cause large changes in resultant coating composition.

This was investigated by measuring the sputtering voltage during deposition, while varying the nitrogen content of the atmosphere to produce curves as depicted in Figure 3. Only the increasing curve is shown, so that the effect of changing nitrogen content may be clearly seen. In production environments it is generally preferred to use the so called "increasing" curve, as this may be accessed more readily after a so called "cleaning run" wherein the system is sputtered in a purely metallic mode to reset the hysteresis mode. These curves are normalised to allow the effect of changing nitrogen content to be clearly seen.

As seen in Figure 3, with oxygen and argon only a very steep curve is produced - solid line - which has an extremely high rate of change. Meanwhile, the addition of 15, 24, 30, and 50 seem of nitrogen each lessens the steepness of the hysteresis curve, and therefore reduces the rate of change. As such, desirable luminescent coatings are more repeatedly produced with a less steep hysteresis curve, which may be influenced by the introduction of increasing amounts of nitrogen to the atmosphere.

For luminescent coatings produced using the experimental method and apparatus a voltage 600

V provided luminescent coatings repeatably, however the voltage will change depending on the coating apparatus and method, particularly the sputtering power. An increased sputtering power, such as that used in a production environment, will result in higher measured sputtering voltages for the metallic mode, and even greater rates of change in the hysteresis curve, making control of the rate of change using nitrogen even more important.

The inventors produced examples 1 to 12 according to the invention, wherein the atmosphere included a proportion of nitrogen based on the total gas flows (N2%) as shown in Table 2. The presence of luminescence was again checked by eye by illuminating with a torch with a UV led bulb 365 nm, and a percentage of nitrogen based on the flow of oxygen and nitrogen calculated (N₂/(N₂+O₂) %).

Table 2

As shown by the examples according to the invention, by incorporating nitrogen into the sputtering atmosphere, coatings that are luminescent may be produced much more consistently, for instance, 12 in 14 runs.

A further 20 examples according to the invention were produced using a sputtering atmosphere with a flow rate percentage of nitrogen based on nitrogen and oxygen of 38% over a two week period, all of which exhibited luminescence. In addition, the inventors produced examples according to the invention which luminesced with flow rate percentages of nitrogen based on nitrogen and oxygen as low as 12%. Such low nitrogen proportions may be controlled by using mixed gas sources, wherein nitrogen is mixed with a noble gas such as argon before reaching the flow controller (either on site or from a gas canister). This leads to unavoidable variations in the flow controller to have a lower overall effect on the gas proportions in the system. As such, preferably the nitrogen flows from a source via a flow controller and the source is a mixed nitrogen and noble gas source, preferably wherein the volume of nitrogen in the source is less than the volume of noble gas, and preferably wherein the noble gas is argon.

Further examples according to the invention were produced, and their composition and luminescence characteristics assessed in more detail.

The composition of the coating layer examples through their thickness was assessed using XPS depth profiling with an x-ray beam (aluminium K-alpha) of spot size of 400pm and an argon ion etch beam operated at 1 KeV (M) producing a beam current of 2.0 pA, the beam rastered over a 2.0 x 4.0mm area of the coating layer. A total etch time of from 1 to 4 hours was used. The binding energy windows used in the acquisition of the profile were: Ols, Cis, Sm3d, Sn3d, AI2p, Si2p, Ca2p, Nls, Nals and Mgls. An average composition is produced by excluding the surface area of the coating layer and the interface with the glass substrate.

The luminescence characteristics of the examples were measured using an edge detection apparatus as depicted in Figure 4.

The edge detection apparatus 1 comprises a glass sample 2 resting on stand-offs 3, within a testing area defined by location pins 4. Below the stand-offs 3 and underneath the whole sample is a piece of black card 5. The glass sample 2 comprising a coating layer is mounted on the standoffs 3 such that a surface comprising a luminescent coating layer - not shown - is orientated away from the black card 5. A photon receiver 6 comprising a cosine corrector - not shown - is mounted on a bracket - not shown - and aligned with and in contact with an edge of the glass sample 2. The photon receiver 6 is connected to a UV filter 11 via an optical fibre 8 and then to a photon counter 7 via a further optical fibre 8.

A black painted box 9 is placed over the glass sample 2, and repeatable positioning is ensured by the location pins 4. A UV 365 nm led lamp 10 is mounted in the black painted box 9 aligned with the centre of the glass sample. The UV led lamp 10 and photon counter 7 are powered by electrical supplies - not shown - and the photon counter is connected to a computer - not shown. During the measurement the UV led lamp 10 illuminates the glass sample 2, causing the luminescent coating layer to luminesce. Photons are internally reflected to the glass substrate 2 edges, and some enter the photon receiver 6, and are passed through a UV filter 11 for removing unabsorbed UV light before being transferred to the photon counter 7 which then communicates with the computer to produce spectra.

Measured spectra were integrated between 660 and 750 nm, to provide a photon count over the luminescent range. It was seen that the luminescent emission increased linearly with increasing thickness of luminescent coating for a given composition. Therefore, the photon count may be divided by the thickness in nm to provide a value of counts per nm which may then be compared between samples. Thickness was measured using a Dektak stylus profilometer.

Table 3

It was discovered that the examples and comparative examples that exhibited luminescence were substoichiometric in oxygen, therefore preferably the coating is substoichiometric in oxygen.

Furthermore, while the presence of nitrogen in the sputtering atmosphere allows luminescent coatings to be repeatedly produced, an increase in the nitrogen content of the layer is associated with a decrease in the luminescence of the coating, as indicated by Table 3. It can be seen that luminescence is reduced significantly for a sputter atmosphere percentage of nitrogen based on nitrogen and oxygen of 39, therefore preferably the percentage of nitrogen based on nitrogen and oxygen is less than 39%, preferably 20% or less.

Examples according to the invention were produced and the luminescence and absorption measured after a heat treatment (5 minutes, 600 °C). As depicted in Figure 5, luminescence decreases and absorption increases with increasing nitrogen percentage based on nitrogen and oxygen in the sputtering atmosphere, with a marked increase above 30% and an inflection point at around 25%. As such, preferably the nitrogen percentage based on nitrogen and oxygen is less than 30%, even more preferably less than 25%. However, less than 10% nitrogen based on nitrogen and oxygen is associated with a reduction in repeatability of production of luminescent coatings, therefore preferably the percentage of nitrogen based on nitrogen and oxygen is 10 % or more, more preferably 12% or more, even more preferably 15% or more.

As such, preferably the percentage of nitrogen based on nitrogen and oxygen is from 10 to 30 % by volume, preferably from 12 to 25% by volume.

Therefore, the inventors have learned that the introduction of nitrogen into the sputtering atmosphere allows luminescent coatings to be produced more consistently, but it is preferable that the minimum proportion of nitrogen is introduced so that the luminescent output is not reduced.

XPS depth profiling of examples measured before and after heat treatment indicated that heat treatment had no significant effect on the composition of the coating layer, other than some migration of sodium from the glass substrate into the lowermost area of the coating layer. It is believed that heat treatment improves the luminescence by altering the distribution within the amorphous layer, rather than its composition.

Claims

1. A method of depositing a coating layer on a substrate comprising the steps of: providing a substrate with a first surface and a second surface; providing a target comprising silicon, aluminium and samarium; and sputtering the target comprising silicon, aluminium and samarium under an atmosphere comprising a noble gas, oxygen and nitrogen to form the coating layer on the first surface of the substrate, wherein the atmosphere comprises a percentage of nitrogen based on nitrogen and oxygen of from 1 to 90% by volume.

2. A method according to claim 1, wherein the atmosphere comprises a percentage of nitrogen based on nitrogen and oxygen of from 5 to 70%, preferably of from 10 to 50%, more preferably of from 12 to 30%, by volume.

3. A method according to claim 1 or claim 2, wherein the target comprises from 85 to 95 wt% silicon, from 5 to 10 wt% aluminium, and from 2 to 4 wt% samarium, preferably wherein the target comprises from 88 to 90 wt% silicon, from 7 to 8 wt% aluminium, and from 3 to 4 wt% samarium.

4. A method according to any preceding claim, wherein the noble gas is argon.

5. A method according to any preceding claim, wherein the substrate comprises glass, preferably glass of thickness from 3 to 15 mm, more preferably 4 to 12 mm, yet more preferably 5 to 10 mm, most preferably glass of thickness from 7 to 9 mm.

6. A method according to any preceding claim, further comprising, after the step comprising sputtering the target comprising silicon, aluminium and samarium, a step of heating the substrate at a temperature in excess of 600 °C, preferably for at least 3 minutes, more preferably for at least 5 minutes; preferably the step of heating the substrate comprises a toughening process.

7. A method according to any preceding claim, further comprising a step of depositing an underlayer prior to the step of sputtering the target comprising silicon, aluminium and samarium, preferably wherein the step of depositing an underlayer comprises sputtering a target comprising silicon. 8. A method according to any preceding claim, wherein a step comprising sputtering comprises voltage controlled deposition.

9. A substrate comprising: a first surface; and a coating layer directly or indirectly upon the first surface, wherein the coating layer comprises silicon, aluminium, samarium, oxygen and nitrogen, and wherein the coating layer comprises an atomic percentage of silicon o, an atomic percentage of aluminium 3, an atomic percentage of samarium £, an atomic percentage of oxygen x, and an atomic percentage of nitrogen y, wherein x > y.

10. A substrate according to claim 9, wherein the atomic percentage of nitrogen y is from 0.1 to 15, preferably y is from 1 to 10, more preferably y is from 2 to 5.

12. A substrate according to claim 9 or claim 10, wherein the coating layer comprises samarium with an oxidation state of 2+, and an atomic percentage of samarium with an oxidation state of 2+ is greater than or equal to an atomic percentage of samarium with an oxidation state of 3+.

13. A substrate according to any of claims 9 to 12, wherein o is from 25 to 40, 3 is from 1 to 5, £ is from 0.01 to 5, and x is from 40 to 70, more preferably wherein o is from 30 to 35, 3 is from 2 to 4, £ is from 0.1 to 0.5, and x is from 50 to 60.

14. A substrate according to any of claims 9 to 13, wherein the coating layer is substoichiometric in oxygen.

15. A substrate according to any of claims 9 to 14, wherein the coating layer has a thickness of from 500 to 5000 nm, preferably from 1000 to 2500 nm, more preferably from 1250 to 2250 nm.

16. A substrate according to any of claims 9 to 15, wherein the substrate comprises glass, preferably glass of thickness from 3 to 15 mm, more preferably from 4 to 12 mm, yet more preferably 5 to 10 mm, most preferably glass of thickness from 7 to 9 mm.

17. A laminated structure comprising a substrate comprising a coating layer deposited according to any of claims 1 to 8, or a substrate according to any of claims 9 to 16, adhered to a sheet of material by an adhesive layer; preferably the adhesive layer comprises polyvinyl butyral (PVB).

18. A laminated structure according to claim 17 wherein the first surface comprising the coating layer is adjacent to the adhesive layer.

19. A laminated structure according to claim 17 or 18, wherein the sheet of material comprises glass, preferably both the substrate and the sheet of material comprise glass.

20. A glazing pane comprising a substrate comprising a coating layer deposited according to any of claims 1 to 8, or a substrate according to any of claims 9 to 16, or a laminated structure according to any of claims 17 to 19.