The isothermal vacuum-induced dehydration of thin films made of poly(methoxy diethylene glycol acrylate) (PMDEGA), which were swollen under ambient conditions, is studied. The dehydration behavior of the homopolymer film as well as of a nanostructured film of the amphiphilic triblock copolymer polystyrene-block-poly(methoxy diethylene glycol acrylate)-block-polystyrene, abbreviated as PS-b-PMDEGA-b-PS, are probed, and compared to the thermally induced dehydration behavior of such thin thermo-responsive films when they pass through their LCST-type coil-to globule collapse transition. The dehydration kinetics is followed by in-situ neutron reflectivity measurements. Contrast results from the use of deuterated water. Water content and film thickness are significantly reduced during the process, which can be explained by Schott second order kinetics theory for both films. The water content of the dehydrated equilibrium state from this model is very close to the residual water content obtained from the final static measurements, indicating that residual water still remains in the film even after prolonged exposure to the vacuum. In the PS-b-PMDEGA-b-PS film that shows micro-phase separation, the hydrophobic PS domains modify the dehydration process by hindering the water removal, and thus retarding dehydration by about 30%. Whereas residual water remains tightly bound in the PMDEGA domains, water is completely removed from the PS domains of the block copolymer film.

The rehydration of thermoresponsive polystyrene-block-poly(methoxy diethylene glycol acrylate)-block-polystyrene (PS-b-PMDEGA-b-PS) films forming a lamellar microphase-separated structure is investigated by in situ neutron reflectivity in a D2O vapor atmosphere. The rehydration of collapsed PS-b-PMDEGA-b-PS films is realized by a temperature change from 45 to 23 degrees C and comprises (1) condensation and absorption of D2O, (2) evaporation of D2O, and (3) reswelling of the film due to internal rearrangement. The hydrophobic PS layers hinder the absorption of condensed D2O, and a redistribution of embedded D2O between the hydrophobic PS layers and the hydrophilic PMDEGA layers is observed. In contrast, the rehydration of semiswollen PS-b-PMDEGA-b-PS films (temperature change from 35 to 23 degrees C) shows two prominent differences: A thicker D2O layer condenses on the surface, causing a more enhanced evaporation of D2O. The rehydrated films differ in film thickness and volume fraction of D2O, which is due to the different thermal protocols, although the final temperature is identical.

The rehydration of thermoresponsive poly(monomethoxydiethylene glycol acrylate) (PMDEGA) films exhibiting a lower critical solution temperature (LCST) type demixing phase transition in aqueous environments, induced by a decrease in temperature, is investigated in situ with real-time neutron reflectivity. Two different starting conditions (collapsed versus partially swollen chain conformation) are compared. In one experiment, the temperature is reduced from above the demixing temperature to well below the demixing temperature. In a second experiment, the starting temperature is below the demixing temperature, but within the transition regime, and reduced to the same final temperature. In both cases, the observed rehydration process can be divided into three stages: first condensation of water from the surrounding atmosphere, then absorption of water by the PMDEGA film and evaporation of excess water, and finally, rearrangement of the PMDEGA chains. The final rehydrated film is thicker and contains more absorbed water as compared with the initially swollen film at the same temperature well below the demixing temperature.

Multi-stage co-evaporation processes for the growth of Cu2ZnSnSe4 (CZTSe) thin films are investigated with time-resolved in situ angle-dispersive X-ray diffraction (in situ XRD). Different preparation protocols were applied and controlled by in situ laser light scattering (in situ LLS). The composition of the deposited layers was adjusted by making use of a stoichiometric transitions in the LLS signal at the point where the Cu content equals the [Zn+Sn]. The ability of in situ XRD to distinguish between CZTSe and ZnSe is used to develop new processes that minimize the formation of ZnSe as a secondary phase. At high temperatures, an initially grown ZnSe layer forms at the Mo interface, which may not be incorporated into the CZTSe due to Zn-rich preparation conditions. By using lower temperatures at the beginning, CZTSe growth starts directly and a heating step restores the high temperature of the substrate. Thus, the formation of secondary phases is diminished without losing the benefits of higher preparation temperature. The ZnSe growth is reduced and the formation of a continuous layer is not observed.

The deposition of a Cu2ZnSnSe4 (CZTSe) thin film with a multi-stage co-evaporation process is investigated with time-resolved in situ X-ray diffraction (in situ XRD). For the experiment a novel setup intended for in situ analysis of thin film deposition processes was used. The in situ data confirm the former observation that CZTSe growth is delayed with deposition of only Cu-2 Se-x and ZnSe in the initial process stage and provide new insight into the evolution of the appearing phases. In Zn-rich deposition conditions, ZnSe deposited at the beginning may not be consumed by the growing CZTSe but remain as an unreacted layer at the interface to the Mo back contact. Cu2-xSe growth starts with the formation of a Cu rich phase, which is reduced to a Cu poor phase in the process. Furthermore, our results show that in situ XRD at elevated temperatures is able to distinguish between ZnSe and CZTSe and that it can be used for the detection of ZnSe as secondary phase. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

physica status solidi (a)Volume 212, Issue 2 p. 356-363 Original Paper Co-evaporation process study of Cu2ZnSnSe4 thin films by in situ light scattering and in situ X-ray diffraction Stefan Hartnauer, Stefan Hartnauer Photovoltaics Group, Martin-Luther-University Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle (Saale), GermanySearch for more papers by this authorLeonard A. Wägele, Leonard A. Wägele Photovoltaics Group, Martin-Luther-University Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle (Saale), GermanySearch for more papers by this authorFrank Syrowatka, Frank Syrowatka Martin-Luther-University Halle-Wittenberg, IZM/Nanotechnikum Weinberg, Heinrich-Damerow-Str. 4, 06120 Halle (Saale), GermanySearch for more papers by this authorGunar Kaune, Gunar Kaune Photovoltaics Group, Martin-Luther-University Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle (Saale), GermanySearch for more papers by this authorRoland Scheer, Corresponding Author Roland Scheer Photovoltaics Group, Martin-Luther-University Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle (Saale), GermanyCorresponding author: e-mail [email protected], Phone: +49 345 5525490, Fax: +49 345 5527354Search for more papers by this author Stefan Hartnauer, Stefan Hartnauer Photovoltaics Group, Martin-Luther-University Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle (Saale), GermanySearch for more papers by this authorLeonard A. Wägele, Leonard A. Wägele Photovoltaics Group, Martin-Luther-University Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle (Saale), GermanySearch for more papers by this authorFrank Syrowatka, Frank Syrowatka Martin-Luther-University Halle-Wittenberg, IZM/Nanotechnikum Weinberg, Heinrich-Damerow-Str. 4, 06120 Halle (Saale), GermanySearch for more papers by this authorGunar Kaune, Gunar Kaune Photovoltaics Group, Martin-Luther-University Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle (Saale), GermanySearch for more papers by this authorRoland Scheer, Corresponding Author Roland Scheer Photovoltaics Group, Martin-Luther-University Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle (Saale), GermanyCorresponding author: e-mail [email protected], Phone: +49 345 5525490, Fax: +49 345 5527354Search for more papers by this author First published: 21 October 2014 https://doi.org/10.1002/pssa.201431497Citations: 2Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Abstract Multi-stage co-evaporation processes for the growth of Cu2ZnSnSe4 (CZTSe) thin films are investigated with time-resolved in situ angle-dispersive X-ray diffraction (in situ XRD). Different preparation protocols were applied and controlled by in situ laser light scattering (in situ LLS). The composition of the deposited layers was adjusted by making use of a stoichiometric transitions in the LLS signal at the point where the Cu content equals the [Zn + Sn]. The ability of in situ XRD to distinguish between CZTSe and ZnSe is used to develop new processes that minimize the formation of ZnSe as a secondary phase. At high temperatures, an initially grown ZnSe layer forms at the Mo interface, which may not be incorporated into the CZTSe due to Zn-rich preparation conditions. By using lower temperatures at the beginning, CZTSe growth starts directly and a heating step restores the high temperature of the substrate. Thus, the formation of secondary phases is diminished without losing the benefits of higher preparation temperature. The ZnSe growth is reduced and the formation of a continuous layer is not observed. References 1 S. Bag, O. Gunawan, T. Gokmen, Y. Zhu, T. K. Todorov, and D. B. Mitzi, Energy Environ. Sci. 5(5), 7060–7065 (2012). 2 T. K. Todorov, J. Tang, S. Bag, O. Gunawan, T. Gokmen, Y. Zhu, and D. B. Mitzi, Adv. Energy Mater. 3(1), 34–38 (2012). 3 W. Wang, M. T. Winkler, O. Gunawan, T. Gokmen, T. K. Todorov, Y. Zhu, and D. B. Mitzi, Adv. Energy Mater. 4, 7 (2014). 4 P. Jackson, D. Hariskos, E. Lotter, S. Paetel, R. Wuerz, R. Menner, W. Wischmann, and M. Powalla, Prog. Photovolt.: Res. Appl. 19(7), 894–897 (2011). 5 B. Shin, O. Gunawan, Y. Zhu, N. A. Bojarczuk, S. Jay Chey, and S. Guha, Prog. Photovolt. 21(1), 72–76 (2013). 6 I. Repins, C. Beall, N. Vora, C. DeHart, D. Kuciauskas, P. Dippo, B. To, J. Mann, W. C. Hsu, A. Goodrich, and R. Noufi, Sol. Energy Mater. Sol. Cells 101, 154–159 (2012). 7 R. Scheer, A. Neisser, K. Sakurai, P. Fons, and S. Niki, Appl. Phys. Lett. 82(13), 2091–2093 (2003). 8 K. Sakurai, R. Scheer, S. Nakamura, Y. Kimura, T. Baba, C. A. Kaufmann, A. Neisser, S. Ishizuka, A. Yamada, K. Matsubara, K. Iwata, P. Fons, H. Nakanishi, and S. Niki, Sol. Energy Mater. Sol. Cells 90(18–19), 3377–3384 (2006). 9 K. Sakurai, T. Neumann, R. Hesse, D. Abou-Ras, P. Jablonski, A. Neisser, C. Kaufmann, S. Niki, R. Scheer, and H. W. Schock, Thin Solid Films 515, (15), 6222–6225 (2007). 10 C. A. Kaufmann, T. Unold, D. Abou-Ras, J. Bundesmann, A. Neisser, R. Klenk, R. Scheer, K. Sakurai, and H. W. Schock, Thin Solid Films 515(15), 6217–6221 (2007). 11 R. Scheer, A. Pérez-Rodríguez, and W. K. Metzger, Prog. Photovolt.: Res. Appl. 18, 467–480 (2010). 12 G. Kaune, S. Hartnauer, F. Syrowatka, and R. Scheer, Sol. Energy Mater. Sol. Cells B 120, 596–602 (2014). 13 A. Redinger, K. Hones, X. Fontane, V. Izquierdo-Roca, E. Saucedo, N. Valle, A. Perez-Rodriguez, and S. Siebentritt, Appl. Phys. Lett. 98(10), 101907 (2011). 14 J. T. Wätjen, J. Engman, M. Edoff, and C. Platzer-Björkman, Appl. Phys. Lett. 100, (17), 173510 (2012). 15 W. C. Hsu, I. Repins, C. Beall, C. DeHart, B. To, G. Teeter, and R. Noufi, Sol. Energy Mater. Sol. Cells 113, 160–164 (2013). 16 P. Fernandes, P. Salome, and A. da Cunha, Thin Solid Films 517(7), 2519–2523 (2009). 17 G. Kaune, S. Hartnauer, and R. Scheer, Phys. Status Solidi A 211(9), 1991–1996 (2014). 18 S. S. Ballard, S. E. Brown, and J. S. Browder, Appl. Opt. 17(7), 1152 (1978). 19 X. He and H. Shen, Phys. Scr. 85, 035302 (2012). 20 I. Repins, D. Fisher, W. Batchelor, L. Woods, and M. Beck, Prog. Photovolt.: Res. Appl. 13(4) 311–323 (2005). 21 A. Redinger and S. Siebentritt, Appl. Phys. Lett. 97(9), 092111 (2010). 22 B. Shin, Y. Zhu, N. A. Bojarczuk, S. J. Chey, and S. Guha, Appl. Phys. Lett. 101, 053903 (2012). Citing Literature Volume212, Issue2February 2015Pages 356-363 ReferencesRelatedInformation

The complex nanomorphology of a defect-rich deuterated poly(styrene-block-methyl methacrylate), P(S-b-MMAd), diblock copolymer film is determined with a combination of grazing-incidence small-angle neutron scattering (GISANS) and time-of-flight (TOF) mode. TOF-GISANS enables the simultaneous performance of several GISANS measurements that differ in wavelength. The resulting set of GISANS data covers different ranges of the scattering vector and has different scattering depths. Thus surface-sensitive and bulk-sensitive measurements can be performed simultaneously. The P(S-b-MMAd) film exhibits a lamellar microphase separation structure, which because of the defects is arranged into small, randomly oriented grains, composed of four–five lamellar repetitions. In the near-surface region, the lamellar structure is oriented parallel to the substrate, which explains the smooth surface found with atomic force microscopy.

The deposition of Cu2ZnSnSe4 (CZTSe) thin films with a two-stage co-evaporation process was investigated with in situ laser light scattering (LLS) and ex situ characterization methods. As a result of the process conditions as well as intrinsic reactions, the film growth is divided into distinct growth phases with characteristic phase formation processes in each phase. In a first phase, under supply of Cu, Zn, Sn and Se, only Cu2−xSe and ZnSe are deposited on the substrate. A film with several hundred nanometer thickness is necessary to initiate the CZTSe formation. Then, in a second phase, CZTSe grows by incorporation of Cu and Sn in ZnSe while Cu2−xSe remains as secondary phase. In the second process stage with terminated Cu evaporation, the remaining Cu2−xSe is consumed and the film stoichiometry turns from Cu-rich to Cu-poor. A substantial influence on the growth process is found for the Mo substrate, CZTSe growth is hindered by a detrimental interaction between Mo and CZTSe. During the whole process, the Cu2−xSe phase plays an important role in the grain growth process and supports the formation of large CZTSe grains.

Cobalt sputter deposition on a nanostructured polystyrene-block-poly(ethylene oxide), P(S-b-EO), template is followed in real time with grazing incidence small-angle X-ray scattering (GISAXS). The polymer template consists of highly oriented parallel crystalline poly(ethylene oxide) (PEO) domains that are sandwiched between two polystyrene (PS) domains. In-situ GISAXS shows that cobalt atoms selectively decorate the PS domains of the microphase-separated polymer film and then aggregate to form surface metal nanopatterns. The polymer template is acting as a directing agent where cobalt metal nanowires are formed. At high metal load, the characteristic selectivity of the template is lost, and a uniform metal layer forms on the polymer surface. During the early stage of cobalt metal deposition, a highly asymmetric nanoparticles agglomeration is dominating structure formation. The cobalt nanoparticles mobility in combination with the high tendency of the nanoparticles to coalescence and to form immobile large-sized particles at the PS domains are discussed as mechanisms of structure formation.

Thin thermoresponsive films of the triblock copolymer polystyrene-block-poly(methoxydiethylene glycol acrylate)-block-polystyrene (P(S-b-MDEGA-b-S)) are investigated on silicon substrates. By spin coating, homogeneous and smooth films are prepared for a range of film thicknesses from 6 to 82 nm. Films are stable with respect to dewetting as investigated with optical microscopy and atomic force microscopy. P(S-b-MDEGA-b-S) films with a thickness of 39 nm exhibit a phase transition of the lower critical solution temperature (LCST) type at 36.5 degrees C. The swelling and the thermoresponsive behavior of the films with respect to a sudden thermal stimulus are probed with in-situ neutron reflectivity. In undersaturated water vapor swelling proceeds without thickness increase. The thermoresponse proceeds in three steps: First, the film rejects water as the temperature is above LCST. Next, it stays constant for 600 s, before the collapsed film takes up water again. With ATR-FTIR measurements, changes of bound water in the film caused by different thermal stimuli are studied. Hydrogen bonds only form between C=O and water in the swollen film. Above the LCST most hydrogen bonds with water are broken, but some amount of bound water remains inside the film in agreement with the neutron reflectivity data. Grazing-incidence small-angle X-ray scattering (GISAXS) shows that the inner lateral structure is not significantly influenced by the different thermal stimuli.

Nanostructured titania films are of growing interest due to their application in future photovoltaic technologies. Therefore, a lot of effort has been put into the controlled fabrication and tailoring of titania nanostructures. The controlled sol-gel synthesis of titania, in particular in combination with block copolymer templates, is very promising because of its high control on the nanostructure, easy application and cheap processing possibilities. This tutorial review gives a short overview of the structural control of titania films gained by using templated sol-gel chemistry and shows how this approach is extended by the addition of further functionality to the films. Different expansions of the sol-gel templating are possible by the fabrication of gradient samples, by the addition of a homopolymer, by the combination with micro-fluidics and also by the application of novel precursors for low-temperature processing. Moreover, hierarchically structured titania films can be fabricated via the subsequent application of several sol-gel steps or via the inclusion of colloidal templates in a one-step process. Integrated function in the block copolymer used in the sol-gel synthesis allows for the fabrication of an integrated blocking layer or an integrated hole-conductor. Both approaches grant a one-step fabrication of two components of a working solar cell, which make them very promising towards a cheap solar cell production route. Looking to the complete solar cell, the top contact is also of great importance as it influences the function of the whole solar cell. Thus, the mechanisms acting in the top contact formation are also reviewed. For all these aspects, characterization techniques that allow for a structural investigation of nanostructures inside the active layers are important. Therefore, the characterization techniques that are used in real space as well as in reciprocal space are explained shortly as well.

The switching kinetics of thin thermo-responsive hydrogel films of poly(monomethoxy-diethyleneglycol-acrylate) (PMDEGA) are investigated. Homogeneous and smooth PMDEGA films with a thickness of 35.9 nm are prepared on silicon substrates by spin coating. As probed with white light interferometry, PMDEGA films with a thickness of 35.9 nm exhibit a phase transition temperature of the lower critical solution temperature (LCST) type of 40 °C. In situ neutron reflectivity is performed to investigate the thermo-responsive behavior of these PMDEGA hydrogel films in response to a sudden thermal stimulus in deuterated water vapor atmosphere. The collapse transition proceeds in a complex way which can be seen as three steps. The first step is the shrinkage of the initially swollen film by a release of water. In the second step the thickness remains constant with water molecules embedded in the film. In the third step, perhaps due to a conformational rearrangement of the collapsed PMDEGA chains, water is reabsorbed from the vapor atmosphere, thereby giving rise to a relaxation process. Both the shrinkage and relaxation processes can be described by a simple model of hydrogel deswelling.

Growth and morphology of an aluminum (Al) contact on a poly(3-hexylthiophene) (P3HT) thin film are investigated with X-ray methods and related to the interactions at the Al:P3HT interface. Grazing incidence small-angle scattering (GISAXS) is applied in situ during Al sputter deposition to monitor the growth of the layer. A growth mode is found, in which the polymer surface is wetted and rapidly covered with a continuous layer. This growth type results in a homogeneous film without voids and is explained by the strong chemical interaction between Al and P3HT, which suppresses the formation of three-dimensional cluster structures. A corresponding three stage growth model (surface bonding, agglomeration, and layer growth) is derived. X-ray reflectivity shows the penetration of Al atoms into the P3HT film during deposition and the presence of a 2 nm thick intermixing layer at the Al:P3HT interface.

The film morphology of thin polymer blend films based on poly[(1-methoxy)-4-(2-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) and poly(N-vinylcarbazole) (PVK) is probed as a function of film thickness. Blend films are prepared with spin-coating of polymer solutions with different concentrations on top of solid supports. The blending ratio of both conducting polymers is kept constant. The film and surface morphology is probed with grazing incidence ultrasmall-angle X-ray scattering (GIUSAXS) and atomic force microscopy (AFM). A linear dependence between the film thickness and the averaged phase separation is found. In addition, X-ray reflectivity measurements show an enrichment of PVK at the substrate interface. UV/vis spectroscopy measurements indicate a linearly increasing amount of both homopolymers in the blend films for increasing film thicknesses. The generalized knowledge about the influence of the film thickness on the phase separation behavior in conducting polymer blend films is finally used to describe the phase separation formation during the spin-coating process, and the results are discussed in the framework of an adapted Flory-Huggins theory for rodlike polymers.

Cobalt (Co) sputter deposition onto a colloidal polymer template is investigated using grazing incidence small-angle X-ray scattering (GISAXS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). SEM and AFM data picture the sample topography, GISAXS the surface and near-surface film structure. A two-phase model is proposed to describe the time evolution of the Co growth. The presence of the colloidal template results in the correlated deposition of an ultrathin Co film on the sample surface and thus in the creation of Co capped polystyrene (PS) colloids. Well below the percolation threshold, the radial growth is restricted and only height growth is observed.

The depth-dependent morphology of the microphase separation structure in thin block copolymer films is examined using non-destructive time-of-flight grazing-incidence small-angle neutron scattering. The structure of a cylinder-forming diblock copolymer, polystyrene(deuterated)- block -polyisoprene, in contact with either a low- or a high-energy substrate surface is investigated. A systematic identification of the components of the polymer film at different depths is achieved by utilizing the material characteristic Yoneda peak. For the polymer film attached to the low-surface-energy aminosilane-coated substrate, a morphology transition from lamellar at the substrate–polymer interface, via perforated lamellar in the film bulk, to an ill-defined structure at the polymer–air interface is observed. This phase transition along the film normal is due to the competition between the surface-induced morphological changes and the stable cylindrical bulk morphology of the diblock copolymer. In contrast, on the high-energy surface no pronounced ordering is found for the applied conditions.

We investigate the formation of an ordered array of metal nanoclusters via selective doping of microphase-separated nanodomains in thin diblock copolymer films. Nanostructure formation during this doping process is probed in situ with microbeam grazing incidence small-angle X-ray scattering (mu GISAXS) and ex-situ with atomic force microscopy (AFM). During sputter deposition of iron on the thin film template of polystyrene-block-poly(methyl methacrylate) P(S-b-MMA) copolymer, having upright cylindrical domains of PMMA, iron atoms selectively dope the PMMA domains due to the preferential chemical affinity. AFM confirms the mu GISAXS results that the iron atoms preferentially wet the PMMA domains at low amount of sputter deposited iron. Up to a threshold of a nominal thickness of 2.0 rim deposited iron, the atoms wet only the PM:MA domains and create the ordered array of metal nanoclusters. Above this threshold thickness the iron nanostructures grow laterally and finally cover the complete template surface.

The structure of porous TiO2 films and TiO2:poly(N-vinylcarbazole) (PVK) composite films is investigated with time-of-flight grazing incidence small-angle neutron scattering (TOF-GISANS). The TiO2 films have been prepared by application of a sol-gel process with a diblock copolymer as structure directing agent, and the conductive polymer PVK is infiltrated in the porous network by spin coating and solution casting. The films show a hierarchical pore structure with mesopores 52 nm in size and additional large macropores with a diameter of about 180 nm. By matching the scattering contrast of the TiO2 with the polymer information about the penetration of the polymer in the pores is determined. Whereas in the PVK film prepared by solution casting the pores are filled to a high degree; in the spin coated film, PVK wets only the TiO2 pore walls and forms a solid overlying layer. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1628-1635,2010