Specific Process Knowledge/Characterization/Stress measurement/Stress origins - Revision history

Reet: /* Metal film stress dependence on composition and growth conditions */

2024-02-09T09:28:06Z

Metal film stress dependence on composition and growth conditions

← Older revision		Revision as of 11:28, 9 February 2024
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	Notice that you can increase the atomic mobility (and reduce the tensile stress) by increasing the temperature. This trend is clearly shown in e.g., Abermann's data. In sputtering you can also increase the mobility of the atoms in the growing films by decreasing the pressure and adding a bias to accelerate the sputtered atoms towards the growing film. In evaporation you can in some cases also add mobility to the growing film by ion bombardment during the deposition.		Notice that you can increase the atomic mobility (and reduce the tensile stress) by increasing the temperature. This trend is clearly shown in e.g., Abermann's data. In sputtering you can also increase the mobility of the atoms in the growing films by decreasing the pressure and adding a bias to accelerate the sputtered atoms towards the growing film. In evaporation you can in some cases also add mobility to the growing film by ion bombardment during the deposition.

			Another way to summarize in general – based on tutorial articles by E Chason and coauthors:
			* Very thin films exhibit tensile stress (island coalescence)
			* Thicker films can be tensile or compressive

			* Tensile tends to occur in low-mobility materials
			* More tensile with fast deposition at low temperature
			* Examples Ni, Cr

			* Compressive stress tends to be in high-mobility materials
			* More compressive with slower deposition at higher temperature
			* Can become less compressive as temp drops at end of deposition
			* Examples Au, Ag, Cu


	==Models of thin film growth and stress==		==Models of thin film growth and stress==

Reet at 10:23, 8 February 2024

2024-02-08T10:23:46Z

← Older revision		Revision as of 12:23, 8 February 2024
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	=~~Stress~~ dependence on ~~film~~ and growth ~~characteristics~~=		=Metal film stress dependence on composition and growth conditions=

Reet: /* Stress dependence on film and growth characteristics */

2024-02-05T12:05:17Z

Stress dependence on film and growth characteristics

← Older revision		Revision as of 14:05, 5 February 2024
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	*Tensile stress is associated with '''low atomic mobility''' and increases when the deposition rate is increased.		*Tensile stress is associated with '''low atomic mobility''' and generally increases when the deposition rate is increased.
	*Compressive stress is associated with '''high atomic mobility''' and ~~will increase~~ when the deposition rate is decreased.		*Compressive stress is associated with '''high atomic mobility''' and generally increases when the deposition rate is decreased.
	\|-		\|-
	\|}		\|}

	This general rule is ~~based on from~~ Abermann's 1990 article, [https://www-sciencedirect-com.proxy.findit.cvt.dk/science/article/pii/0042207X9093933A Measurements of the intrinsic stress in thin metal films]. ~~It means the~~ stress depends both on inherent material properties and on deposition conditions, as one would probably also expect intuitively.		This general rule is described, e.g., in Abermann's 1990 article, [https://www-sciencedirect-com.proxy.findit.cvt.dk/science/article/pii/0042207X9093933A Measurements of the intrinsic stress in thin metal films]. The article describes how thin film stress depends both on inherent material properties and on deposition conditions, as one would probably also expect intuitively.

	Materials that tend to exhibit tensile stress were called Type I materials by Abermann. They have comparatively low atomic mobility and high melting points and include Cr, Ni, and Pt.		Materials that tend to exhibit tensile stress were called Type I materials by Abermann. They have comparatively low atomic mobility and high melting points and include Cr, Ni, and Pt.
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	Materials that tend to exhibit compressive stress were called Type II materials by Abermann. They have comparatively high atomic mobility and low melting point and include Au, Cu, Al, and Ag.		Materials that tend to exhibit compressive stress were called Type II materials by Abermann. They have comparatively high atomic mobility and low melting point and include Au, Cu, Al, and Ag.

	The melting point does not predict the stress behavior of a material all that well, however. Abermann's own data show that Au (mp 1065 °C) has more compressive stress than Al (mp 660 °C) despite a higher melting point, and internal Nanolab data show that Ti (mp 1660 °C) has more compressive stress than Au. So other factors are at play, as has been described by other authors. For instance, all other things being equal the tensile stress decreases or the compressive stress increases with smaller grain size, according to E. Chason and collaborators. Since large grains gives more tensile stress and the grain size tends to increase for thicker layers, the tensile stress will tend to increase when a thicker layer is grown. This is apparently especially true for the many metals with low mobility that tend to form columnar grains during thin film growth.		The melting point does not predict the stress behavior of a material all that well, however. Abermann's own data show that Au (mp 1065 °C) has more compressive stress than Al (mp 660 °C) despite a higher melting point, and internal Nanolab data show that Ti (mp 1660 °C) has more compressive stress than Au. So other factors are at play, as has been described by other authors. For instance, all other things being equal the tensile stress decreases or the compressive stress increases with smaller grain size, according to E. Chason and collaborators (see references below). Since large grains gives more tensile stress and the grain size tends to increase for thicker layers, the tensile stress will tend to increase when a thicker layer is grown. This is apparently especially true for the many metals with low mobility that tend to form columnar grains during thin film growth.

	You can read more about the model of thin film stress developed by E. Chason and collaborators at Brown university in their many publications including [https://pubs.aip.org/aip/jap/article/119/19/191101/1032395/Tutorial-Understanding-residual-stress-in this tutorial].		You can read more about the model of thin film stress developed by E. Chason and collaborators at Brown university in their many publications including [https://pubs.aip.org/aip/jap/article/119/19/191101/1032395/Tutorial-Understanding-residual-stress-in this tutorial].

Reet: /* Stress dependence on film and growth characteristics */

2024-02-02T13:47:28Z

Stress dependence on film and growth characteristics

← Older revision		Revision as of 15:47, 2 February 2024
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	In the page [[Specific Process Knowledge/Characterization/Stress measurement\|overview page on stress measurement]] you can find links to studies made at DTU Nanolab about specific deposition results with our own sputter and e-beam evaporation systems. This page aims to give more general information about the origin of stress in thin films. It appears that the following is a good rule of thumb~~, though it does not completely match the concrete observations for the sputtered films referred to above~~:		In the page [[Specific Process Knowledge/Characterization/Stress measurement\|overview page on stress measurement]] you can find links to studies made at DTU Nanolab about specific deposition results with our own sputter and e-beam evaporation systems. This page aims to give more general information about the origin of stress in thin films. It appears that the following is a good rule of thumb:

	{\| border="1" style="width: 100 %; background:#C1C1C1"		{\| border="1" style="width: 100 %; background:#C1C1C1"
	\|-		\|-
	\|		\|
	*Tensile stress ~~tends to increase when there~~ is low atomic mobility and ~~high~~ deposition rate		*Tensile stress is associated with '''low atomic mobility''' and increases when the deposition rate is increased.
	*Compressive stress ~~tends to increase when there~~ is high atomic mobility and ~~low~~ deposition rate		*Compressive stress is associated with '''high atomic mobility''' and will increase when the deposition rate is decreased.
	\|-		\|-
	\|}		\|}

	This means the stress depends both on inherent material properties and on deposition conditions.		This general rule is based on from Abermann's 1990 article, [https://www-sciencedirect-com.proxy.findit.cvt.dk/science/article/pii/0042207X9093933A Measurements of the intrinsic stress in thin metal films]. It means the stress depends both on inherent material properties and on deposition conditions, as one would probably also expect intuitively.

	~~Examples of~~ materials ~~with~~ comparatively ~~high~~ atomic mobility include Au, Cu, and ~~Ag. They will tend to exhibit more compressive stress~~.		Materials that tend to exhibit tensile stress were called Type I materials by Abermann. They have comparatively low atomic mobility and high melting points and include Cr, Ni, and Pt.

	~~Examples of~~ materials ~~with~~ comparatively ~~low~~ atomic mobility include Cr, ~~Ni -~~ and ~~Pt??. They will tend to exhibit more tensile stress~~.		Materials that tend to exhibit compressive stress were called Type II materials by Abermann. They have comparatively high atomic mobility and low melting point and include Au, Cu, Al, and Ag.

	~~First-hand evidence of~~ the ~~differences in~~ stress ~~in these materials is~~ that Cr and ~~Ni layers in combination~~ with ~~other metal~~ layers in the ~~PVD equipment at Nanolab cause~~ a ~~lot of flaking~~.		The melting point does not predict the stress behavior of a material all that well, however. Abermann's own data show that Au (mp 1065 °C) has more compressive stress than Al (mp 660 °C) despite a higher melting point, and internal Nanolab data show that Ti (mp 1660 °C) has more compressive stress than Au. So other factors are at play, as has been described by other authors. For instance, all other things being equal the tensile stress decreases or the compressive stress increases with smaller grain size, according to E. Chason and collaborators. Since large grains gives more tensile stress and the grain size tends to increase for thicker layers, the tensile stress will tend to increase when a thicker layer is grown. This is apparently especially true for the many metals with low mobility that tend to form columnar grains during thin film growth.

	You can ~~increase~~ the ~~atomic mobility (and reduce the tensile~~ stress) by ~~increasing the temperature~~. ~~In sputtering you can decrease the pressure~~ and ~~add a bias to accelerate the sputtered atoms towards the growing film for increased mobility~~. ~~In evaporation you could add mobility to the growing film by using an increased substrate temperature or by ion bombardment during the deposition~~.		You can read more about the model of thin film stress developed by E. Chason and collaborators at Brown university in their many publications including [https://pubs.aip.org/aip/jap/article/119/19/191101/1032395/Tutorial-Understanding-residual-stress-in this tutorial].

	~~In addition, all other things being equal~~ the tensile stress ~~decreases/compressive stress increases with smaller grain size~~. ~~The grain size tends to~~ increase ~~for thicker layers, meaning that~~ the ~~tensile stress will tend~~ to ~~increase when a thicker layer is grown~~. ~~This is apparently especially true for the many metals with low~~ mobility ~~that tend~~ to ~~form columnar grains~~ during ~~thin film growth~~.		Notice that you can increase the atomic mobility (and reduce the tensile stress) by increasing the temperature. This trend is clearly shown in e.g., Abermann's data. In sputtering you can also increase the mobility of the atoms in the growing films by decreasing the pressure and adding a bias to accelerate the sputtered atoms towards the growing film. In evaporation you can in some cases also add mobility to the growing film by ion bombardment during the deposition.

	==Models of thin film growth and stress==		==Models of thin film growth and stress==
	The text above is based on a model of thin film stress developed by E. Chason and collaborators at Brown university. You can read about it in their many publications including [https://pubs.aip.org/aip/jap/article/119/19/191101/1032395/Tutorial-Understanding-residual-stress-in this tutorial].

	~~The main~~ explanation for the origin of tensile stress in thin films is that ~~these~~ films start growing as islands rather than as a continuous atomic layer. The surface energy of these islands is reduced when islands ~~grow together~~, which makes up for the energy needed to exhibit tensile stress.		According to the Abermann article, the tutorial mentioned above, and [https://pubs.aip.org/avs/jva/article/36/2/020801/246484/Review-Article-Stress-in-thin-films-and-coatings this review], the explanation for the origin of tensile stress in thin films is that most films start growing as islands rather than as a continuous atomic layer. The surface energy of these islands is reduced when islands unite into a layer, which makes up for the energy needed to exhibit tensile stress (initially when there is no film but only small islands, there is no stress).

	The origin of the compressive stress is controversial but ~~might have~~ to do with grain growth and densification of the film, especially in columnar growth of materials that are capped by an oxide layer.		The origin of the compressive stress is apparently more controversial (according to the group at Brown) but presumably has to do with the energetics of grain growth and densification of the film, especially in columnar growth of materials that are capped by an oxide layer.

	An interesting observation also seen here at Nanolab is that stress in thin films can change significantly over time ''after the end of the deposition''. In some materials this occurs over the course of days not just minutes - apparently this can, e.g., take place in nickel and in gold, see, e.g., articles about TiPtAu and TiPt contacts on III-V materials.		An interesting observation also seen here at Nanolab is that stress in thin films can change significantly over time ''after the end of the deposition''. In some materials this occurs over the course of days not just minutes - apparently this can, e.g., take place in nickel and in gold, see, e.g., articles about TiPtAu and TiPt contacts on III-V materials (references coming soon!).

	To learn more generally about stress in thin films, we recommend the classical article by John A. Thornton and D. W. Hoffman from 1979, [https://www.sciencedirect.com/science/article/pii/0040609089900308 Stress-related effects in thin films], and other articles by the same ~~author~~. The tutorial by E. Chason refers back to the model of thin film growth developed in that paper.		To learn more generally about stress in thin films, we recommend the classical article by John A. Thornton and D. W. Hoffman from 1979, [https://www.sciencedirect.com/science/article/pii/0040609089900308 Stress-related effects in thin films], and other articles by the same authors. The tutorial by E. Chason refers back to the model of thin film growth developed in that paper.

	''Note this page is in progress - comments are very welcome.''		''Note this page is in progress - comments are very welcome.''

Reet at 13:05, 2 February 2024

2024-02-02T13:05:39Z

← Older revision		Revision as of 15:05, 2 February 2024
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	'''Feedback to this page''': '''[mailto:labadviser@nanolab.dtu.dk?Subject=Feed%20back%20from%20page%20http://labadviser.nanolab.dtu.dk/index.php/Specific_Process_Knowledge/Characterization/Stress_measurement/~~Stress _origins~~ click here]'''		'''Feedback to this page''': '''[mailto:labadviser@nanolab.dtu.dk?Subject=Feed%20back%20from%20page%20http://labadviser.nanolab.dtu.dk/index.php/Specific_Process_Knowledge/Characterization/Stress_measurement/Stress_origins click here]'''

	<i> This page is written by Rebecca Ettlinger, a member of the <b>DTU Nanolab staff</b></i>		<i> This page is written by Rebecca Ettlinger, a member of the <b>DTU Nanolab staff</b></i>

Reet: /* Models of thin film growth and stress */

2024-01-22T14:44:06Z

Models of thin film growth and stress

← Older revision		Revision as of 16:44, 22 January 2024
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	To learn more generally about stress in thin films, we recommend the classical article by John A. Thornton and D. W. Hoffman from 1979, [https://www.sciencedirect.com/science/article/pii/0040609089900308 Stress-related effects in thin films], and other articles by the same author. The tutorial by E. Chason refers back to the model of thin film growth developed in that paper.		To learn more generally about stress in thin films, we recommend the classical article by John A. Thornton and D. W. Hoffman from 1979, [https://www.sciencedirect.com/science/article/pii/0040609089900308 Stress-related effects in thin films], and other articles by the same author. The tutorial by E. Chason refers back to the model of thin film growth developed in that paper.

	'Note this page is in progress - comments are very welcome.'		''Note this page is in progress - comments are very welcome.''

Reet: /* Stress dependence on film characteristics */

2024-01-22T14:43:51Z

Stress dependence on film characteristics

← Older revision		Revision as of 16:43, 22 January 2024
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	=Stress dependence on film characteristics=		=Stress dependence on film and growth characteristics=

Reet: /* Stress dependence on film characteristics */

2024-01-22T14:42:28Z

Stress dependence on film characteristics

Reet: /* Stress dependence on film characteristics */

2024-01-12T14:40:59Z

Stress dependence on film characteristics

← Older revision		Revision as of 16:40, 12 January 2024
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	In the page about [[Specific Process Knowledge/Thin film deposition/Lesker/Stress dependence on sputter parameters in the Lesker sputter system\|stress dependence on sputter parameters for Si, Ni, and Cu]] you can read some recommendations about which sputter parameters led to which stress characteristics in specific materials.		In the page about [[Specific Process Knowledge/Thin film deposition/Lesker/Stress dependence on sputter parameters in the Lesker sputter system\|stress dependence on sputter parameters for Si, Ni, and Cu]] you can read some recommendations about which sputter parameters led to which stress characteristics in specific materials.

	This page aims to give more general information about the origin of stress in thin films. It appears that the following is a good rule of thumb		This page aims to give more general information about the origin of stress in thin films. It appears that the following is a good rule of thumb, though it does not completely match the concrete observations for the sputtered films referred to above:
	{\| border="1" style="width: 100 %; background:#C1C1C1"		{\| border="1" style="width: 100 %; background:#C1C1C1"
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Reet: /* Stress dependence on film characteristics */

2024-01-12T14:35:32Z

Stress dependence on film characteristics

← Older revision		Revision as of 16:35, 12 January 2024
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	This means the stress depends both on inherent material properties and on deposition conditions.		This means the stress depends both on inherent material properties and on deposition conditions.

	Examples of materials with comparatively high atomic mobility include Au, Cu, and Ag.		Examples of materials with comparatively high atomic mobility include Au, Cu, and Ag. They will tend to exhibit more compressive stress.

	Examples of materials with comparatively low atomic mobility include Cr, Ni, and Pt.		Examples of materials with comparatively low atomic mobility include Cr and Ni - and Pt and Ru??. They will tend to exhibit more tensile stress.

			The differences in stress in these materials is definitely something we can recognize from first-hand experience at Nanolab, as Cr and Ni layers in combination with other metal layers in the PVD equipment cause a lot of flaking.

	You can increase the atomic mobility (and reduce the tensile stress) by increasing the temperature, and in sputtering you can decrease the pressure and add a bias to accelerate the sputtered atoms towards the growing film. In evaporation you could potentially add energy to the growing film by using ion bombardment apart from increased deposition temperature.		You can increase the atomic mobility (and reduce the tensile stress) by increasing the temperature, and in sputtering you can decrease the pressure and add a bias to accelerate the sputtered atoms towards the growing film. In evaporation you could potentially add energy to the growing film by using ion bombardment apart from increased deposition temperature.
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	In addition, all other things being equal the tensile stress decreases/compressive stress increases with smaller grain size. The grain size tends to increase for thicker layers, meaning that the tensile stress will tend to increase when a thicker layer is grown. This is apparently especially true for the many metals with low mobility that tend to form columnar grains during thin film growth.		In addition, all other things being equal the tensile stress decreases/compressive stress increases with smaller grain size. The grain size tends to increase for thicker layers, meaning that the tensile stress will tend to increase when a thicker layer is grown. This is apparently especially true for the many metals with low mobility that tend to form columnar grains during thin film growth.

			==Models of thin film growth and stress==
	These observations are based on a model of thin film stress developed by E. Chason and collaborators at Brown university. You can read about it in their many publications including [https://pubs.aip.org/aip/jap/article/119/19/191101/1032395/Tutorial-Understanding-residual-stress-in this tutorial].		These observations are based on a model of thin film stress developed by E. Chason and collaborators at Brown university. You can read about it in their many publications including [https://pubs.aip.org/aip/jap/article/119/19/191101/1032395/Tutorial-Understanding-residual-stress-in this tutorial].

← Older revision		Revision as of 16:42, 22 January 2024
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	In the page ~~about~~ [[Specific Process Knowledge/~~Thin film deposition/Lesker~~/Stress ~~dependence~~ on ~~sputter parameters in the Lesker sputter system\|~~stress ~~dependence on sputter parameters for Si, Ni, and Cu~~]] you can ~~read some recommendations~~ about ~~which~~ sputter ~~parameters led to which stress characteristics in specific materials~~.		In the page [[Specific Process Knowledge/Characterization/Stress measurement\|overview page on stress measurement]] you can find links to studies made at DTU Nanolab about specific deposition results with our own sputter and e-beam evaporation systems. This page aims to give more general information about the origin of stress in thin films. It appears that the following is a good rule of thumb, though it does not completely match the concrete observations for the sputtered films referred to above:

	This page aims to give more general information about the origin of stress in thin films. It appears that the following is a good rule of thumb, though it does not completely match the concrete observations for the sputtered films referred to above:
	{\| border="1" style="width: 100 %; background:#C1C1C1"		{\| border="1" style="width: 100 %; background:#C1C1C1"
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	Examples of materials with comparatively high atomic mobility include Au, Cu, and Ag. They will tend to exhibit more compressive stress.		Examples of materials with comparatively high atomic mobility include Au, Cu, and Ag. They will tend to exhibit more compressive stress.

	Examples of materials with comparatively low atomic mobility include Cr ~~and~~ Ni - and Pt ~~and Ru~~??. They will tend to exhibit more tensile stress.		Examples of materials with comparatively low atomic mobility include Cr, Ni - and Pt??. They will tend to exhibit more tensile stress.

	~~The~~ differences in stress in these materials is ~~definitely something we can recognize from first-hand experience at Nanolab, as~~ Cr and Ni layers in combination with other metal layers in the PVD equipment cause a lot of flaking.		First-hand evidence of the differences in stress in these materials is that Cr and Ni layers in combination with other metal layers in the PVD equipment at Nanolab cause a lot of flaking.

	You can increase the atomic mobility (and reduce the tensile stress) by increasing the temperature~~, and in~~ sputtering you can decrease the pressure and add a bias to accelerate the sputtered atoms towards the growing film. In evaporation you could ~~potentially~~ add ~~energy~~ to the growing film by using ion bombardment ~~apart from increased~~ deposition ~~temperature~~.		You can increase the atomic mobility (and reduce the tensile stress) by increasing the temperature. In sputtering you can decrease the pressure and add a bias to accelerate the sputtered atoms towards the growing film for increased mobility. In evaporation you could add mobility to the growing film by using an increased substrate temperature or by ion bombardment during the deposition.

	In addition, all other things being equal the tensile stress decreases/compressive stress increases with smaller grain size. The grain size tends to increase for thicker layers, meaning that the tensile stress will tend to increase when a thicker layer is grown. This is apparently especially true for the many metals with low mobility that tend to form columnar grains during thin film growth.		In addition, all other things being equal the tensile stress decreases/compressive stress increases with smaller grain size. The grain size tends to increase for thicker layers, meaning that the tensile stress will tend to increase when a thicker layer is grown. This is apparently especially true for the many metals with low mobility that tend to form columnar grains during thin film growth.

	==Models of thin film growth and stress==		==Models of thin film growth and stress==
	~~These observations are~~ based on a model of thin film stress developed by E. Chason and collaborators at Brown university. You can read about it in their many publications including [https://pubs.aip.org/aip/jap/article/119/19/191101/1032395/Tutorial-Understanding-residual-stress-in this tutorial].		The text above is based on a model of thin film stress developed by E. Chason and collaborators at Brown university. You can read about it in their many publications including [https://pubs.aip.org/aip/jap/article/119/19/191101/1032395/Tutorial-Understanding-residual-stress-in this tutorial].

	The main explanation for the origin of tensile stress in thin films is that these films start growing as islands rather than as a continuous atomic layer. The surface energy of these islands is reduced when islands grow together, which makes up for the energy ~~associated with~~ tensile stress ~~appearing~~.		The main explanation for the origin of tensile stress in thin films is that these films start growing as islands rather than as a continuous atomic layer. The surface energy of these islands is reduced when islands grow together, which makes up for the energy needed to exhibit tensile stress.

	The origin of the compressive stress is controversial but might have to do with grain growth and densification especially in columnar growth of materials capped by an oxide layer.		The origin of the compressive stress is controversial but might have to do with grain growth and densification of the film, especially in columnar growth of materials that are capped by an oxide layer.

	~~All this also points to an~~ interesting observation~~: Stress~~ in thin films can change significantly over time after the end of the deposition. In some ~~(high mobility)~~ materials this ~~might be~~ over the course of days not just minutes - apparently this can e.g. take place in gold, see, e.g., articles about TiPtAu and TiPt contacts on III-V materials.		An interesting observation also seen here at Nanolab is that stress in thin films can change significantly over time ''after the end of the deposition''. In some materials this occurs over the course of days not just minutes - apparently this can, e.g., take place in nickel and in gold, see, e.g., articles about TiPtAu and TiPt contacts on III-V materials.

	To learn more generally about stress in thin films, we ~~also~~ recommend the classical article by John A. Thornton and D. W. Hoffman from 1979, [https://www.sciencedirect.com/science/article/pii/0040609089900308 Stress-related effects in thin films], and other articles by the same author. The tutorial by E. Chason refers back to the model of thin film growth developed in that paper.		To learn more generally about stress in thin films, we recommend the classical article by John A. Thornton and D. W. Hoffman from 1979, [https://www.sciencedirect.com/science/article/pii/0040609089900308 Stress-related effects in thin films], and other articles by the same author. The tutorial by E. Chason refers back to the model of thin film growth developed in that paper.

	'Note this page is in progress - comments are very welcome.'		'Note this page is in progress - comments are very welcome.'