Name: cooling rate dependent ellipsometry measurements to determine the dynamics of thin glassy films
Uploaded: 2016-01-26T18:00:00
Description: Watch this Scientific Journal Video about Cooling Rate Dependent Ellipsometry Measurements to Determine the Dynamics of Thin Glassy Films at JoVE.com

The Authors would like to acknowledge James A. Forrest for help in the initial idea for this technique.26&#160;This work was supported by funding from the University of Pennsylvania and was partially supported by the MRSEC program of the National Science Foundation under award no. DMR-11- 20901 at the University of Pennsylvania.

1. Film Preparation
<ol>
	<li>Weigh 0.04 g of polystyrene, and place into a 30 ml vial.</li>
	<li>Weigh 2 g of toluene into the vial. A 2% by weight solution of polystyrene in toluene yields a film of approximately 100 nm.</li>
	<li>Let the solution sit O/N to fully dissolve the polystyrene and let the solutions settle.</li>
	<li>Place a 1 cm x 1 cm Silicon (Si) wafer onto a Spin Coater.</li>
	<li>Spin the wafer at 8,000 rpm for 45 sec. While it is spinning, drop approximately 1 ml of toluene on the spinning wafer.<br ...

<ol>
	<li>Keddie, J. L., Jones, R. A. L., Cory, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Size-Dependent+depression+of+the+glass+transition+temperature+in+polymer+films.">Size-Dependent depression of the glass transition temperature in polymer films.</a> Europhys. Lett. 27 (1), 59-64 (1994).</li><li>Forrest, J. A., Veress, K. D., Dutcher, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interface+and+chain+confinement+effects+on+the+glass+transition+temperature+of+thin+polymer+films.">Interface and chain confinement effects on the glass transition temperature of thin polymer films.</a> Phys. Rev.E. 56 (5), 5705-5716 (1997).</li><li>Forrest, J. A., Mattsson, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reductions+of+the+glass+transition+temperature+in+thin+polymer+films:+Probing+the+length+scale+of+cooperative+dynamics.">Reductions of the glass transition temperature in thin polymer films: Probing the length scale of cooperative dynamics.</a> Phys. Rev.E. 61 (1), R53-R56 (2000).</li><li>Sharp, J. S., Forrest, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Free+surfaces+cause+reductions+in+the+glass+transition+temperature+of+thin+polystyrene+films.">Free surfaces cause reductions in the glass transition temperature of thin polystyrene films.</a> PRL. 91 (23), 235701 (2003).</li><li>Ellison, C. J., Torkelson, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+distribution+of+glass-transition+temperatures+in+nanoscopically+confined+glass+formers.">The distribution of glass-transition temperatures in nanoscopically confined glass formers.</a> Nat. Mat. 2 (10), 695-700 (2003).</li><li>Priestley, R. D., Ellison, C. J., Broadbelt, L. J., Torkelson, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+relaxation+of+polymer+glasses+at+surfaces,+interfaces,+and+in+between.">Structural relaxation of polymer glasses at surfaces, interfaces, and in between.</a> Science. 309 (5733), 456-459 (2005).</li><li>Ellison, C. J., Kim, S. D., Hall, D. B., Torkelson, J. 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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impacts+of+polystyrene+molecular+weight+and+modification+to+the+repeat+unit+structure+on+the+glass+Transition&#8722;Nanoconfinement+effect+and+the+cooperativity+length+scale.">Impacts of polystyrene molecular weight and modification to the repeat unit structure on the glass Transition&#8722;Nanoconfinement effect and the cooperativity length scale.</a> Macromolecules. 38 (5), 1767-1778 (2005).</li><li>Yang, Z., Fujii, Y., Lee, F. K., Lam, C. H., Tsui, O. K. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glass+transition+dynamics+and+surface+layer+mobility+in+unentangled+polystyrene+films.">Glass transition dynamics and surface layer mobility in unentangled polystyrene films.</a> Science. 328 (5986), 1676-1679 (2010).</li><li>Tsui, O. K. C., Zhang, H. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+chain+ends+and+chain+entanglement+on+the+glass+transition+temperature+of+polymer+thin+films.">Effects of chain ends and chain entanglement on the glass transition temperature of polymer thin films.</a> Macromolecules. 34 (26), 9139-9142 (2001).</li><li>Roth, C. B., Dutcher, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glass+Transition+and+Chain+Mobility+in+thin+Polymer+Films.">Glass Transition and Chain Mobility in thin Polymer Films.</a> J. Electroanal. Chem. 584, 13-22 (2005).</li><li>Ediger, M. D., Forrest, J. 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A., Schick, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+AC-chip+calorimeter+for+glass+transition+measurements+in+ultrathin+films.">Differential AC-chip calorimeter for glass transition measurements in ultrathin films.</a> J. Polym. Sci. B. 44 (20), 2996-3005 (2006).</li><li>Tress, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glassy+dynamics+in+condensed+isolated+polymer+chains.">Glassy dynamics in condensed isolated polymer chains.</a> Science. 341 (6152), 1371-1374 (2013).</li><li>Boucher, V. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=T+g+depression+and+invariant+segmental+dynamics+in+polystyrene+thin+films.">T g depression and invariant segmental dynamics in polystyrene thin films.</a> Soft Matter. 8 (19), 5119-5122 (2012).</li><li>Yu, M., Olson, E. A., Zhang, M., Zhang, Z., Allen, L. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glass+transition+in+ultrathin+polymer+films:+Calorimetric+study.">Glass transition in ultrathin polymer films: Calorimetric study.</a> PRL. 91 (8), 085703 (2003).</li><li>Kremer, F., Tress, M., Mapesa, E. U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glassy+dynamics+and+glass+transition+in+nanometric+layers+and+films:+A+silver+lining+on+the+horizon.">Glassy dynamics and glass transition in nanometric layers and films: A silver lining on the horizon.</a> J. Non-Crys. Solids. 407, 277-283 (2015).</li><li>Qi, D., Ilton, M., Forrest, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measuring+surface+and+bulk+relaxation+in+glassy+polymers.">Measuring surface and bulk relaxation in glassy polymers.</a> Euro. Phys. J. E. 34 (6), 1-7 (2011).</li><li>Teichroeb, J. H., Forrest, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+imaging+of+nanoparticle+embedding+to+probe+viscoelasticity+of+polymer+surfaces.">Direct imaging of nanoparticle embedding to probe viscoelasticity of polymer surfaces.</a> PRL. 91 (1), 016104 (2003).</li><li>Fakhraai, Z., Forrest, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measuring+the+surface+dynamics+of+glassy+polymers.">Measuring the surface dynamics of glassy polymers.</a> Science. 319 (5863), 600-604 (2008).</li><li>Paeng, K., Swallen, S. F., Ediger, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+measurement+of+molecular+motion+in+freestanding+polystyrene+thin+films.">Direct measurement of molecular motion in freestanding polystyrene thin films.</a> J. Am. Chem. Soc. 133 (22), 8444-8447 (2011).</li><li>Glor, E. C., Fakhraai, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Facilitation+of+interfacial+dynamics+in+entagled+polymer+films.">Facilitation of interfacial dynamics in entagled polymer films.</a> JCP. 141 (9), 194505 (2014).</li><li>Fakhraai, Z., Forrest, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+slow+dynamics+in+supported+thin+polymer+films.">Probing slow dynamics in supported thin polymer films.</a> PRL. 95 (2), 025701 (2005).</li><li>Roth, C. B., McNerny, K. L., Jager, W. F., Torkelson, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Eliminating+the+enhanced+mobility+at+the+free+surface+of+polystyrene:+fluorescence+studies+of+the+glass+transition+temperature+in+thin+bilayer+films+of+immiscible+polymers.">Eliminating the enhanced mobility at the free surface of polystyrene: fluorescence studies of the glass transition temperature in thin bilayer films of immiscible polymers.</a> Macromolecules. 40 (7), 2568-2574 (2007).</li><li>Priestley, R. D., Ellison, C. J., Broadbelt, L. J., Torkelson, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+relaxation+of+polymer+glasses+at+surfaces,+interfaces,+and+in+between.">Structural relaxation of polymer glasses at surfaces, interfaces, and in between.</a> Science. 309 (5733), 456-459 (2005).</li><li>Gao, S., Koh, Y. P., Simon, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calorimetric+Glass+Transition+of+Single+Polystyrene+Ultrathin+Films.">Calorimetric Glass Transition of Single Polystyrene Ultrathin Films.</a> Macromolecules. 46 (92), 562-570 (2013).</li><li>Tropin, T. V., Schulz, G., Schmelzer, J. W. P., Schick, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heat+capacity+measurements+and+modeling+of+polystyrene+glass+transition+in+a+wide+range+of+cooling+rates.">Heat capacity measurements and modeling of polystyrene glass transition in a wide range of cooling rates.</a> J. Non-Cryst. Solids. 409, 63-75 (2015).</li><li>Kim, S., Hewlett, S. A., Roth, C. B., Torkelson, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Confinement+effects+of+glass+transition+temperature,+transition+breadth,+and+expansivity:+Comparison+of+ellipsometry+and+fluorescence+measurements+on+polystyrene+films.">Confinement effects of glass transition temperature, transition breadth, and expansivity: Comparison of ellipsometry and fluorescence measurements on polystyrene films.</a> Eur. Phys. J.E. 30, 83-92 (2009).</li><li>Schawe, J. E. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vitrification+in+a+wide+cooling+rate+range:+The+relations+between+cooling+rate,+relaxation+time,+transition+width+and+fragility.">Vitrification in a wide cooling rate range: The relations between cooling rate, relaxation time, transition width and fragility.</a> JCP. 141, 184905 (2014).</li><li>Donth, E., Korus, J., Hempel, E., Beiner, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+DSC+heating+rate+and+HCS+frequency+at+the+glass+transition.">Comparison of DSC heating rate and HCS frequency at the glass transition.</a> Thermochimica Acta. 304-305, 239-249 (1997).</li><li>Zhang, C., Guo, Y., Priestley, R. 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Cooling-Rate dependent Tg measurements are high throughput characterization experiments that can determine the Tg, the expansion coefficient of the glass and the super-cooled liquid, the temperature dependence of the average dynamics, and the fragility of a particular glassy material in a single experiment. Furthermore, unlike fluorescence, embedding, or nanohole relaxation experiments, CR-Tg experiments are relatively quick and simple because they do not utilize fluorophores or other com...

The seminal work of Keddie Jones and Corey1 showed that the glass transition temperature (Tg) of ultra-thin polystyrene films decreases with respect to the bulk value at thicknesses lower than 60 nm. Ever since, many experimental studies2-11 have supported the hypothesis that the observed reductions in Tg are caused by a layer of enhanced mobility near the free surface of these films. However, these experiments are indirect measures of a single relaxation time, and thus there is a debate12-18 centered on a direct correlation between average thin film dynamics and the dynamics at the air/polymer interface.
To answer this debate, many studies have directly measured the dynamics of the free surface (&#964;surface). Nanoparticle embedding,19,20 nanohole relaxation,21 and fluorescence22 studies show that the air/polymer interface has dynamics orders of magnitude faster than the bulk alpha relaxation time (&#964;&#945;) with a much weaker temperature dependence than that of &#964;&#945;. Because of its weak temperature dependence, the &#964;surface of these films,19-22 and enhanced dynamics of thin polystyrene films,23,24 intersects the bulk alpha relaxation (&#964;&#945;) at a single point T*, which is a few degrees above Tg, and at a &#964;&#945; of &#8776; 1 sec. The presence of T* could explain why experiments which probe relaxation times faster than * fail to see any thickness dependence on the Tg of ultra-thin Polystyrene films.13-18 Lastly, while direct measurements of the enhanced mobile layer show that it has a thickness of 4-8 nm,20-22 there is evidence that the propagation length of the dynamics at the air/polymer interface is much larger than the thickness of the mobile surface layer.5,25,26
This report aims to fully describe a protocol for using ellipsometry for cooling rate dependent Tg (CR-Tg) experiments. CR-Tg have been previously used to describe the average dynamics of ultra-thin films of polystyrene.23,24,27,28 Furthermore, This technique was recently used to show a direct correlation between the average dynamics in ultra-thin polystyrene films, and the dynamics at the free surface.23 The advantage of CR-Tg measurements over other types of measurements such as fluorescence, nanoparticle embedding, nanohole relaxation, nanocalorimetry, dielectric spectroscopy, and Brillouin light scattering, studies is that they are relatively quick and simple experiments that do not utilize fluorophores or other complicated experimental techniques. Recent advances in spectroscopic ellipsometry allow this technique to be used to efficiently determine the optical properties of ultra-thin films of polymers and other types of hybrid materials with exceptional accuracy. As such, this technique probes the average dynamics of technologically applicable thin films in temperature and time regimes relevant to the glass transition (T &#8804; Tg, &#964;&#945; &#8805; 100 sec). Furthermore, this technique will provide information on the expansion coefficients of the glassy and supper cooled liquid states as well as the fragility of the system, which can then be compared with data for bulk films. Lastly, CR- Tg experiments can be used for any glassy system so long as the integrity of the film remains throughout the experiment.

<table border="0" cellpadding="0" cellspacing="0" width="918">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Toluene</td>
			<td style="width:111px;">Sigma Aldrich</td>
			<td style="width:119px;">179418-1L</td>
			<td style="width:472px;">This can be purchased from any chemical company.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Atactic Polystyrene</td>
			<td style="width:111px;">Polymer Source Inc.</td>
			<td style="width:119px;">P-4092-S</td>
			<td>This can be purchased from any chemical company.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">THMS 600 temperature stage</td>
			<td style="width:111px;">Linkam</td>
			<td style="width:119px;">THMS 600</td>
			<td>any temperature stage that can be fit to an ellipsometer could be used.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">M2000V Spectroscopic Ellipsometer</td>
			<td style="width:111px;">J.A. Woollam</td>
			<td style="width:119px;">M200V</td>
			<td>This procedure should be applicable for any spectroscopic ellipsometer.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Spin Coater</td>
			<td style="width:111px;">Laurell Technologies</td>
			<td style="width:119px;">WS-650-23B</td>
			<td>This Procedure is possible with any spin coater</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sample vials</td>
			<td style="width:111px;">Fisher Scientific</td>
			<td style="width:119px;">02-912-379</td>
			<td>Any sample vials will do</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Silicon wafers</td>
			<td style="width:111px;">Virginia semi conductors</td>
			<td style="width:119px;">325S1410694D</td>
			<td></td>
		</tr>
	</tbody>
</table>

cooling rate dependent ellipsometry measurements to determine the dynamics of thin glassy films

This report aims to fully describe the experimental technique of using ellipsometry for cooling rate dependent Tg (CR-Tg) experiments. These measurements are simple high-throughput characterization experiments, which can determine the glass transition temperature (Tg), average dynamics, fragility and the expansion coefficient of the super-cooled liquid and glassy states for a variety of glassy materials. This technique allows for these parameters to be measured in a single experiment, while other methods must combine a variety of different techniques to investigate all of these properties. Measurements of dynamics close to Tg are particularly challenging. The advantage of cooling rate dependent Tg measurements over other methods which directly probe bulk and surface relaxation dynamics is that they are relatively quick and simple experiments, which do not utilize fluorophores or other complicated experimental techniques. Furthermore, this technique probes the average dynamics of technologically relevant thin films in temperature and relaxation time (&#964;&#945;) regimes relevant to the glass transition (&#964;&#945; &#62; 100 sec). The limitation to using ellipsometry for cooling rate dependent Tg experiments is that it cannot probe relaxation times relevant to measurements of viscosity (&#964;&#945; &#60;&#60; 1 sec). Other cooling rate dependent Tg measurement techniques, however, can extend the CR-Tg method to faster relaxation times. Furthermore, this technique can be used for any glassy system so long as the integrity of the film remains throughout the experiment.

Fitting Raw Ellipsometry Data
Polystyrene films are transparent in the wavelength range of the ellipsometer (500-1,600 nm). Thus a Cauchy model is a good model for describing the index of refraction of polystyrene films. Figure 1A shows an example of &#936;(&#955;) and &#916;(&#955;) for a thick (274 nm) film of polystyrene, and the resulting fit to the Cauchy model <img alt="Equation 1" src="/f...

Watch this Scientific Journal Video about Cooling Rate Dependent Ellipsometry Measurements to Determine the Dynamics of Thin Glassy Films at JoVE.com

Cooling Rate Dependent Ellipsometry Measurements to Determine the Dynamics of Thin Glassy Films

Here, we present a protocol for cooling rate dependent ellipsometry experiments, which can determine the glass transition temperature (Tg), average dynamics, fragility and the expansion coefficient of the super-cooled liquid and glass for a variety of glassy materials.

This report aims to fully describe the experimental technique of using ellipsometry for cooling rate dependent Tg (CR-Tg) experiments. These measurements ...

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