Next Article in Journal
Mechanistic Study of the Spiroindolones: A New Class of Antimalarials
Next Article in Special Issue
Specific Binding of Anionic Porphyrin and Phthalocyanine to the G-Quadruplex with a Variety of in Vitro and in Vivo Applications
Previous Article in Journal
Ameliorative Effects of Curculigoside from Curculigo orchioides Gaertn on Learning and Memory in Aged Rats
Previous Article in Special Issue
Determination of the Optical GAP in Thin Films of Amorphous Dilithium Phthalocyanine Using the Tauc and Cody Models
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Molecules
Volume 17
Issue 9
10.3390/molecules170910119
molecules-logo
Submit to this Journal Review for this Journal Edit a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Dry Etching of Copper Phthalocyanine Thin Films: Effects on Morphology and Surface Stoichiometry

by 1 and
Michael J. Brett
1,2,*
1
Department of Electrical and Computer Engineering, University of Alberta, Edmonton, AB T6G 2V4, Canada
2
NRC-National Institute for Nanotechnology, Edmonton, AB T6G 2M9, Canada
*
Author to whom correspondence should be addressed.
Molecules 2012, 17(9), 10119-10130; https://doi.org/10.3390/molecules170910119
Received: 16 July 2012 / Revised: 16 August 2012 / Accepted: 20 August 2012 / Published: 24 August 2012
(This article belongs to the Special Issue Tetrapyrroles, Porphyrins and Phthalocyanines)
Browse Figures
Versions Notes

Abstract

:
We investigate the evolution of copper phthalocyanine thin films as they are etched with argon plasma. Significant morphological changes occur as a result of the ion bombardment; a planar surface quickly becomes an array of nanopillars which are less than 20 nm in diameter. The changes in morphology are independent of plasma power, which controls the etch rate only. Analysis by X-ray photoelectron spectroscopy shows that surface concentrations of copper and oxygen increase with etch time, while carbon and nitrogen are depleted. Despite these changes in surface stoichiometry, we observe no effect on the work function. The absorbance and X-ray diffraction spectra show no changes other than the peaks diminishing with etch time. These findings have important implications for organic photovoltaic devices which seek nanopillar thin films of metal phthalocyanine materials as an optimal structure.

Graphical Abstract

1. Introduction

Ion sputtering is often employed by surface analysis techniques, such as auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and sary ion mass spectrometry (SIMS), to generate depth profiles of multilayer films. The limits imposed on depth profiling by the effects of ion sputtering on surface topography have been studied thoroughly for many metal and semiconductor thin films [1,2,3,4,5,6,7,8,9,10,11]. Ripples and cones are among the most common surface features produced by ion bombardment. The severity of surface topography changes during ion sputtering depends on the characteristics of the sample and the ion beam, and can often be reduced by means of sample rotation [5,12,13]. Accurate depth profiling of polymer and organic layers is considerably more challenging than inorganic materials, but has been improved as of late [14,15,16,17,18,19,20]. Few studies have been done on plasma etched metal phthalocyanine (MPc) films, and the effects on morphology are not well known.
This paper investigates the evolution of copper phthalocyanine (CuPc) and zinc phthalocyanine (ZnPc) thin films as they are etched with argon and oxygen plasmas. Significant morphological changes occur as a result of the ion bombardment: A planar surface becomes an array of nanopillars with sub-20 nm diameters. This result is intriguing from an organic photovoltaic perspective, where nanopillar film morphologies are desired whose pillar diameters closely match the short exciton diffusion lengths of around 15 nm seen in organic materials [21]. Many methods have been used to attempt this nanopillar morphology, such as solvent annealing [22], solvent recrystallization [23], organic vapor phase deposition [24], glancing angle deposition [25,26,27,28,29], substrate seeding [30,31], and heat treatments [32,33]. However, nanopillar films remain much less than 100 nm in thickness in most cases, which leaves absorption insufficient for achieving optimal device efficiencies. Therefore, alternative methods are desired for fabricating nanopillar organic films. Plasma etching presents an entirely new approach to structuring organic thin films at the nanoscale. In previous studies, ion bombardment has been found to induce surface texturing on various inorganic materials, which is often explained by the preferential erosion of grain boundaries [2,34,35]. The results presented in this paper exhibit similar behavior, enabling a new approach to nanostructuring MPc thin films.

2. Results and Discussion

2.1. Columnar MPc Film Morphologies via Plasma Etching

The first nanopillar films were fabricated by etching a set of 180 nm thick planar CuPc films with argon plasma. Films were etched with an RF power of 220 W for 20 and 40 ss, resulting in the columnar morphologies seen in Figure 1. With column diameters of around 20 nm or less, these morphologies are smaller than the columns found in the best small molecule films produced to date [33], and are extremely well suited to the exciton diffusion lengths of MPc materials. In addition, the etched columns in Figure 1c are wide at the base and taper off at the top, which may improve their survivability during the solution-based filling processes commonly used in OPV device fabrication.
Etching with oxygen gas instead of argon was also performed, with a chamber pressure of 150 mTorr, RF power of 220 W, and gas flow rate of 80 sccm. The results are shown in Figure 2. Here, etching proceeded much faster due to the reactivity of ionized oxygen, which enhances removal of organic material in conjunction with physical sputtering. A somewhat similar final morphology can be achieved with oxygen plasma compared to argon plasma, albeit with a more disordered and fragile network of remaining features. The likelihood of chemical changes to the film is higher with oxygen, making oxygen plasma etched films less interesting than argon plasma etched films. As such, argon was determined to be the etching gas of choice, and no additional oxygen-etched films were investigated.
Molecules 17 10119 g001 550
Figure 1. Effects of argon plasma etching on a planar CuPc thin film.
Figure 1. Effects of argon plasma etching on a planar CuPc thin film.
Molecules 17 10119 g001
Molecules 17 10119 g002 550
Figure 2. Effects of oxygen plasma etching on a planar CuPc thin film.
Figure 2. Effects of oxygen plasma etching on a planar CuPc thin film.
Molecules 17 10119 g002
The RF power was varied to investigate the sensitivity of morphology to the etch conditions. A 300 nm planar film was exposed to argon plasmas for various periods of time with three levels of RF power: 73 W, 147 W, and 220 W. The images shown in Figure 3 reveal similar etching behavior in all cases, only at different rates. Etched films resembled others that were etched to similar depths under different conditions. Thus, the etching mechanism remains the same, and changes in RF power affect the etch rate only.
Molecules 17 10119 g003 550
Figure 3. Effects of different etch conditions and etch times on the morphology of CuPc thin films etched with argon plasma.
Figure 3. Effects of different etch conditions and etch times on the morphology of CuPc thin films etched with argon plasma.
Molecules 17 10119 g003
It may be possible to further improve these etched film morphologies by starting with an already textured MPc film. For example, glancing angle deposition (GLAD) has been used previously to grow nanopillar MPc films suitable for OPV devices [25,26,27,28,29]. GLAD is a physical vapor deposition technique that produces nanopillar film morphologies by placing the substrate at an oblique angle relative to incoming vapor flux [36]. Combining GLAD with plasma etching could introduce additional control over columnar dimensions and spacing, while requiring less etching and disturbance of the original film. Alternatively, this approach can be thought of as a way to refine the structure of a GLAD film via ion bombardment, which is not an entirely new concept. In fact, ion milling and reactive ion etching have been shown previously to enhance the morphology and properties of GLAD films for various inorganic materials in other applications [37,38,39,40,41]. Figure 4 shows the effects of etching a 120 nm GLAD ZnPc film. The original film has a slanted post morphology (pointing into the page), which appears largely untouched by a low power etch but deteriorates significantly under a more aggressive etch (Figure 4b vs. 4c), with an overall thinning of the areal density of posts observed. In these cases, any structural enhancements due to etching are not obvious. It is possible that a vertical post morphology may be more receptive to plasma etch refinements, and that thicker films with broader columns would benefit more, but this will require further study.
Molecules 17 10119 g004 550
Figure 4. Effects of different argon plasma etching conditions on a thin GLAD ZnPc film.
Figure 4. Effects of different argon plasma etching conditions on a thin GLAD ZnPc film.
Molecules 17 10119 g004

2.2. Surface Analysis and Electronic Properties

The creation of columnar film morphologies out of planar ones with ion sputtering potentially affects the surface composition. The harmful effects of UV radiation from the plasma alone may impact the survivability of the sample [42,43]. In addition, when considering that the ion energies from the plasma are at least comparable to or greater than the intramolecular bond energies in metal phthalocyanines, changes in surface composition may be expected [44,45]. Unsurprisingly, ion beams with MeV ion energies have been shown to be very destructive to MPc molecules [46]. However, the strong π network of MPc molecules may help them avoid fragmentation from impacts of only tens of eV, due to protection by delocalized electrons [47].
The surfaces of the etched CuPc films in this investigation were analyzed with ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS). The UPS curves, shown in Figure 5, show virtually no change in the onset energy for electron ejection, at around 16.5 eV. Consequently, the work function is consistent across all samples, at 4.7 ± 0.1 eV, which is slightly higher than other published values [48,49], but may be simply due to more air exposure [50]. These results provide little insight into the effects of etching, and direct contact resistance measurements could not be performed due to the mechanical sensitivity of the nanopillar films. However, analysis by XPS reveals more significant information.
Molecules 17 10119 g005 550
Figure 5. Changes to the UPS spectra of a planar CuPc film due to argon plasma etching.
Figure 5. Changes to the UPS spectra of a planar CuPc film due to argon plasma etching.
Molecules 17 10119 g005
The atomic concentrations of various elements were calculated from the relative XPS peak heights, and are presented in Figure 6. Significant and immediate removal of C and N is evident in the sample etched for 10 s, which does not change much further in the 30 s etch. Meanwhile, higher concentrations of Cu are revealed by the etching, which is consistent with results from other etch chemistries [45]. Evidently, the CuPc molecules are not surviving the impacts of the Ar ions, and lighter elements are being preferentially removed over heavier ones. Interestingly, a significant amount of O and F are introduced to the surface, which are likely the result of residual gases in the etch chamber binding to the fragmented molecules as a means of stabilization. For device quality CuPc it may be necessary to perform the etching in a UHV environment. The composition of the original planar CuPc film is independent of the incident beam angle, which suggests that the surface and subsurface are very similar. For the etched films, however, the surface is slightly richer in Cu while being depleted of C and N, which confirms the preferential removal of C and N over Cu mentioned previously. These changes to surface composition may impact potential functionality of the CuPc nanopillars at the active layer interface of an OPV device.
Molecules 17 10119 g006 550
Figure 6. Changes to the surface composition of a planar CuPc film due to argon plasma etching.
Figure 6. Changes to the surface composition of a planar CuPc film due to argon plasma etching.
Molecules 17 10119 g006

2.3. Bulk Film Analysis

The surface composition modifications shown in the previous section warrant a study of the bulk properties of the remaining film. Absorbance profiles were gathered in both the visible and infrared spectral regions, which are shown in Figure 7 and Figure 8, respectively. In both cases, no changes to the shape of the absorbance spectra are seen as a result of the etching, but only diminished peak heights. This is consistent with the removal of material seen by SEM, and confirms that much of the remaining film avoids being damaged. Likewise, the X-ray diffraction (XRD) profiles shown in Figure 9 show no changes other than peaks diminishing with etch time. Thus, the material that does remain in the film appears to maintain both its molecular and crystalline structure. It is significant to note that the most etched CuPc film in Figure 7 maintains comparable absorbance to a 120 nm planar un-etched film. Therefore, these films possess nearly the same amount of CuPc material, equivalent to six times the amount used in a typical bilayer OPV device [21]. This confirms that the film morphology seen in Figure 3c is suitable as an ideal OPV active layer architecture. Every point of light absorption in this nanopillar film would be within a single exciton diffusion length of the donor/acceptor interface, and the film would capture significantly more incident light than a commonly used 20 nm planar layer. If the interface were functional, the architecture fabricated by plasma etching would be very useful.
Molecules 17 10119 g007 550
Figure 7. Changes to thin film absorbance as a result of argon plasma etching.
Figure 7. Changes to thin film absorbance as a result of argon plasma etching.
Molecules 17 10119 g007
Alternative sputtering techniques may enable structuring of MPc films while minimizing surface damage. Recently, C60 ion beams have been used to minimize sputtering damage to organic films during analysis [16,17,18,19,20]. Increasing the incident angle of the ion beam has been found to further minimize sputtering damage [20].
Molecules 17 10119 g008 550
Figure 8. Changes to FTIR absorbance spectra of a CuPc thin film due to 220 W argon plasma etching.
Figure 8. Changes to FTIR absorbance spectra of a CuPc thin film due to 220 W argon plasma etching.
Molecules 17 10119 g008
Molecules 17 10119 g009 550
Figure 9. Changes to the XRD spectrum of a planar CuPc thin film as a result of 220 W argon plasma etching.
Figure 9. Changes to the XRD spectrum of a planar CuPc thin film as a result of 220 W argon plasma etching.
Molecules 17 10119 g009
Coincidentally, C60 is the acceptor molecule commonly used with MPc materials in the active layer of small molecule OPV devices. This may be very suitable if ion energies are used that are conducive to maintaining molecular structure, particularly since any residue in the film from the ion beam may be functional in the active layer. Therefore, attempting damage-free, ion-induced structuring of MPc films with C60 is worthy of further investigation.

3. Experimental

CuPc and ZnPc were purchased from Sigma-Aldrich (Oakville, ON, Canada) and purified via thermal gradient sublimation prior to deposition. Both planar and GLAD thin films were deposited in a standard GLAD apparatus [36] via thermal evaporation, with a throw distance of 34 cm, a source temperature of about 400 °C, a base pressure of 2 × 10−7 Torr, and a deposition rate of 0.7 Ǻ/s normal to the surface. A variety of substrates were used, to enable various characterization techniques. ITO-coated glass (Delta Technologies, 8–12 Ω/®) was used for imaging via SEM; Si wafers (Evergreen Semiconductor Materials) were used for analysis by XRD, XPS, and UPS; KBr discs (Fisher Scientific) were used to gather FTIR profiles; and glass microscope slides (Fisher Scientific) were used for UV/Vis absorbance profiles. Argon plasma etching was performed in an Oxford Plasmalab μEtch RIE chamber, with 110 sccm Ar gas flow and a chamber pressure of 190 mTorr. The standard RF power used was 220 W, but was changed on occasion, as explained in the text.
Electron microscope images were acquired using a Hitachi field emission S-4800 SEM. XPS was performed at high vacuum (<5 × 10−10 Torr) with a Kratos Ultra spectrometer, using a Al Kα radiation source (hν = 1,486.71 eV). Measurements were done using incident beam angles of 0° and 60° to probe different surface depths. Atomic concentrations were calculated using the relative peak intensities while accounting for the atomic sensitivity factors. UPS was performed in the same environment as XPS, using a He I (hν = 21.21 eV) radiation source. Absorbance over visible regions was acquired as the negative logarithm of transmittance, using a Perkin Elmer Lambda 900 UV/VIS/NIR spectrophotometer. Infrared absorbance was captured with a Nicolet Nexus 760 FTIR spectrometer with a DTGS detector and a sample chamber purged with N2. XRD data was collected with a Bruker D8 diffractometer, equipped with a Cu source and area detector, and calibrated against a silver behenate reference standard.

4. Conclusions

This paper investigated the effects of argon plasma etching on metal phthalocyanine thin films. Planar films of these materials are readily transformed into nanopillar films with dimensions extremely well suited to OPV devices. The films maintain much of their original molecular characteristics, such as absorbance profiles and crystalline order. However, changes to the surface composition suggest that the ion bombardment causes fragmentation of the molecules at the film surface. Avoiding or repairing this surface damage is necessary to enable functionality in OPV devices, which could provide a new approach to building idealized organic photovoltaic architectures.

Acknowledgments

The authors acknowledge the gracious financial support of the Natural Sciences and Engineering Research Council of Canada (NSERC), Alberta Innovates Technology Futures (AITF), Micralyne Inc., the University of Alberta, and the National Research Council-National Institute for Nanotechnology (NRC-NINT). JV acknowledges NSERC, AITF, SPIE, and the Golden Key International Honour Society for scholarship support. The authors also thank Michael Fleischauer for XRD analysis, the NINT microscopy group, the University of Alberta Nanofab, and the Alberta Centre for Surface Engineering and Science (ACSES) for XPS and UPS analysis.

References

  1. Nobes, M.J.; Colligon, J.S.; Carter, G. The equilibrium topography of sputtered amorphous solids. J. Mater. Sci. 1969, 4, 730–733. [Google Scholar] [CrossRef]
  2. Auciello, O.; Kelly, R. Ion Bombardment Modification of Surfaces; Elsevier Publishing Co.: Amsterdam, The Netherlands, 1984. [Google Scholar]
  3. King, B.V.; Tsong, I.S.T. The depth resolution of sputter profiling. Ultramicroscopy 1984, 14, 75–78. [Google Scholar] [CrossRef]
  4. Tanemura, M.; Okuyama, F. Topographical features of N2+-Sputtered Metal Sandwiches: Their Correlation with Auger Depth Resolution. Thin Solid Films 1988, 165, 193–209. [Google Scholar] [CrossRef]
  5. Cirlin, E.-H.; Vajo, J.J.; Doty, R.E.; Hasenberg, T.C. Ion-induced topography, depth resolution, and ion yield during sary ion mass spectrometry depth profiling of a GaAs/AlGaAs superlattice: Effects of sample rotation. J. Vac. Sci. Technol. A 1991, 9, 1395–1401. [Google Scholar] [CrossRef]
  6. Hofmann, S. Approaching the limits of high resolution depth profiling. Appl. Surf. Sci. 1993, 70–71, 9–19. [Google Scholar] [CrossRef]
  7. Carter, G. The effects of ion bombardment sputtering and atomic transport related roughening and smoothing on depth profiling resolution. Vacuum 1996, 47, 409–420. [Google Scholar] [CrossRef]
  8. Carter, G. The physics and applications of ion beam erosion. J. Phys. D Appl. Phys. 2001, 34, R1–R22. [Google Scholar] [CrossRef]
  9. Karmakar, P.; Mollick, S.A.; Ghose, D.; Chakrabarti, A. Role of initial surface roughness on ion induced surface morphology. Appl. Phys. Lett. 2008, 93, 103102. [Google Scholar] [CrossRef]
  10. Sulania, I.; Tripathi, A.; Kabiraj, D.; Lequeux, M.; Avasthi, D. Surface patterning on indium phosphide with low energy Ar atoms bombardment: an evolution from nanodots to nanoripples. Adv. Mat. Lett. 2010, 1, 118–122. [Google Scholar] [CrossRef]
  11. Zhang, K.; Brötzmann, M.; Hofsäss, H. Surfactant-driven self-organized surface patterns by ion beam erosion. New J. Phys. 2011, 13, 013033. [Google Scholar]
  12. Pamler, W.; Wangemann, K.; Kampermann, S.; Hosler, W. Depth Resolution in Auger Depth Profile Analysis of Aluminum Metallization in Microelectronics: The Effect of Crystalline Texture. Nucl. Instrum. Methods 1990, 51, 34–40. [Google Scholar] [CrossRef]
  13. Tanemura, M.; Fujimoto, S.; Okuyama, F. Dependence of Auger Depth Resolution and Surface Texturing on Primary Ion Species. Surf. Sci. 1990, 230, 283–289. [Google Scholar] [CrossRef]
  14. Cramer, H.-G.; Grehl, T.; Kollmer, F.; Moellers, R.; Niehuis, E.; Rading, D. Depth profiling of organic materials using improved ion beam conditions. Appl. Surf. Sci. 2008, 255, 966–969. [Google Scholar]
  15. Ninomiya, S.; Ichiki, K.; Yamada, H.; Nakata, Y.; Seki, T.; Aoki, T.; Matsuo, J. Molecular depth profiling of multilayer structures of organic semiconductor materials by sary ion mass spectrometry with large argon cluster ion beams. Rapid Commun. Mass Spectrom. 2009, 23, 3264–3268. [Google Scholar] [CrossRef]
  16. Weibel, D.E.; Lockyer, N.; Vickerman, J.C. C60 cluster ion bombardment of organic surfaces. Appl. Surf. Sci. 2004, 231–232, 153–158. [Google Scholar]
  17. Jones, E.A.; Fletcher, J.S.; Thompson, C.E.; Jackson, D.A.; Lockyer, N.P.; Vickerman, J.C. ToF-SIMS analysis of bio-systems: Are polyatomic primary ions the solution? Appl. Surf. Sci. 2006, 252, 6844–6854. [Google Scholar] [CrossRef]
  18. Winograd, N.; Postawa, Z.; Cheng, J.; Szakal, C.; Kozole, J.; Garrison, B.J. Improvements in SIMS continue—Is the end in sight? Appl. Surf. Sci. 2006, 252, 6836–6843. [Google Scholar]
  19. Shon, H.K.; Lee, T.G.; Kim, D.H.; Kang, H.J.; Lee, B.H.; Sung, M.M.; Moon, D.W. The effect of C60 cluster ion beam bombardment in sputter depth profiling of organic–inorganic hybrid multiple thin films. Appl. Surf. Sci. 2008, 255, 1055–1057. [Google Scholar]
  20. Miyayama, T.; Sanada, N.; Iida, S.-I.; Hammond, J.S.; Suzuki, M. The effect of angle of incidence to low damage sputtering of organic polymers using a C60 ion beam. Appl. Surf. Sci. 2008, 255, 951–953. [Google Scholar] [CrossRef]
  21. Yang, F.; Forrest, S.R. Photocurrent generation in nanostructured organic solar cells. ACS Nano 2008, 2, 1022–1032. [Google Scholar] [CrossRef]
  22. Placencia, D.; Wang, W.; Shallcross, R.C.; Nebesny, K.W.; Brumbach, M.; Armstrong, N.R. Organic Photovoltaic Cells Based On Solvent-Annealed, Textured Titanyl Phthalocyanine/C60 Heterojunctions. Adv. Funct. Mater. 2009, 19, 1913–1921. [Google Scholar] [CrossRef]
  23. Karak, S.; Ray, S.K.; Dhar, A. Improvement of efficiency in solar cells based on vertically grown copper phthalocyanine nanorods. J. Phys. D Appl. Phys. 2010, 43, 245101. [Google Scholar] [CrossRef]
  24. Yang, F.; Shtein, M.; Forrest, S.R. Controlled growth of a molecular bulk heterojunction photovoltaic cell. Nat. Mater. 2005, 4, 37–41. [Google Scholar] [CrossRef]
  25. Van Dijken, J.G.; Fleischauer, M.D.; Brett, M.J. Morphology control of CuPc thin films using Glancing Angle Deposition. In Proceedings of 33rd IEEE Photovoltaic Specialists Conference, San Diego, CA, USA, 11–16 May 2008; pp. 1222–1225.
  26. Zheng, Y.; Bekele, R.; Ouyang, J.; Xue, J. Organic photovoltaic cells with vertically aligned crystalline molecular nanorods. Org. Electron. 2009, 10, 1621–1625. [Google Scholar] [CrossRef]
  27. Li, N.; Forrest, S.R. Tilted bulk heterojunction organic photovoltaic cells grown by oblique angle deposition. Appl. Phys. Lett. 2009, 95, 123309. [Google Scholar]
  28. Van Dijken, J.G.; Fleischauer, M.D.; Brett, M.J. Controlled nanostructuring of CuPc thin films via glancing angle deposition for idealized organic photovoltaic architectures. J. Mater. Chem. 2011, 21, 1013–1019. [Google Scholar]
  29. Van Dijken, J.G.; Fleischauer, M.D.; Brett, M.J. Solvent effects on ZnPc thin films and their role in fabrication of nanostructured organic solar cells. Org. Electron. 2011, 12, 2111–2119. [Google Scholar]
  30. Hirade, M.; Nakanotani, H.; Yahiro, M.; Adachi, C. Formation of organic crystalline nanopillar arrays and their application to organic photovoltaic cells. ACS Appl. Mater. Interfaces 2011, 3, 80–83. [Google Scholar] [CrossRef]
  31. Van Dijken, J.G.; Wu, N.L.-Y.; Fleischauer, M.D.; Buriak, J.M.; Brett, M.J. Morphology control and nanoscale patterning of small molecule organic thin films. SPIE 2012, 8435, 8435. [Google Scholar]
  32. Pfuetzner, S.; Mickel, C.; Jankowski, J.; Hein, M.; Meiss, J.; Schuenemann, C.; Elschner, C.; Levin, A.A.; Rellinghaus, B.; Leo, K.; et al. The influence of substrate heating on morphology and layer growth in C60:ZnPc bulk heterojunction solar cells. Org. Electron. 2011, 12, 435–441. [Google Scholar] [CrossRef]
  33. Matsuo, Y.; Sato, Y.; Niinomi, T.; Soga, I.; Tanaka, H.; Nakamura, E. Columnar structure in bulk heterojunction in solution-processable three-layered p-i-n organic photovoltaic devices using tetrabenzoporphyrin precursor and silylmethyl[60]fullerene. J. Am. Chem. Soc. 2009, 131, 16048–16050. [Google Scholar]
  34. Auciello, O. Ion interaction with solids: Surface texturing, some bulk effects, and their possible applications. J. Vac. Sci. Technol. 1981, 19, 841–867. [Google Scholar] [CrossRef]
  35. Cuomo, J.J.; Rossnagel, S.M.; Kaufman, H.R. Handbook of Ion Beam Processing Technology—Principles, Deposition, Film Modification and Synthesis; Noyes Publications: Park Ridge, NJ, USA, 1989. [Google Scholar]
  36. Hawkeye, M.M.; Brett, M.J. Glancing angle deposition: Fabrication, properties, and applications of micro- and nanostructured thin films. J. Vac. Sci. Technol. A 2007, 25, 1317–1335. [Google Scholar] [CrossRef]
  37. Sorge, J.B.; Brett, M.J. Film morphology modification in ion-assisted glancing angle deposition. Thin Solid Films 2010, 519, 1356–1360. [Google Scholar] [CrossRef]
  38. Taschuk, M.T.; Sorge, J.B.; Steele, J.J.; Brett, M.J. Ion-Beam Assisted Glancing Angle Deposition for Relative Humidity Sensors. IEEE Sens. J. 2008, 8, 1521–1522. [Google Scholar] [CrossRef]
  39. Kupsta, M.R.; Taschuk, M.T.; Brett, M.J.; Sit, J.C. Reactive Ion Etching of Columnar Nanostructured TiO2 Thin Films for Modified Relative Humidity Sensor Response Time. IEEE Sens. J. 2009, 9, 1979–1986. [Google Scholar] [CrossRef]
  40. Kwan, J.K.; Sit, J.C. The use of ion-milling to control clustering of nanostructured, columnar thin films. Nanotechnology 2010, 21, 295301. [Google Scholar] [CrossRef]
  41. Jim, S.R.; Oko, A.J.; Taschuk, M.T.; Brett, M.J. Morphological modification of nanostructured ultrathin-layer chromatography stationary phases. J. Chromatogr. A 2011, 1218, 7203–7210. [Google Scholar] [CrossRef]
  42. Peters, C.H.; Sachs-Quintana, I.T.; Kastrop, J.P.; Beaupré, S.; Leclerc, M.; McGehee, M.D. High Efficiency Polymer Solar Cells with Long Operating Lifetimes. Adv. Energy Mater. 2011, 1, 491–494. [Google Scholar] [CrossRef]
  43. Jørgensen, M.; Norrman, K.; Krebs, F.C. Stability/degradation of polymer solar cells. Sol. Energy Mater. Sol. Cells 2008, 92, 686–714. [Google Scholar] [CrossRef]
  44. Naddaf, M.; Chakane, S.; Jain, S.; Bhoraskar, S.V.; Mandale, A.B. Modification of sensing properties of metallophthalocyanine by an ECR plasma. Nucl. Instrum. Meth. B 2002, 194, 54–60. [Google Scholar] [CrossRef]
  45. Pakhomov, G.L.; Drozdov, M.N.; Vostokov, N.V. Plasma irradiation effects in phthalocyanine films. Appl. Surf. Sci. 2004, 230, 241–248. [Google Scholar] [CrossRef]
  46. Kaplan, M.L.; Forrest, S.R.; Schmidt, P.H.; Venkatesan, T. Optical and electrical properties of ion-beam-irradiated films of organic molecular solids and polymers. J. Appl. Phys. 1984, 55, 732. [Google Scholar]
  47. Nath, A.; Prushan, M.J.; Gilbert, J.G. Can super-excited molecules survive fragmentation? J. Radioanal. Nucl. Chem. 2001, 247, 589–591. [Google Scholar] [CrossRef]
  48. Wei, H.X.; Li, J.; Xu, Z.Q.; Cai, Y.; Tang, J.X.; Li, Y.Q. Thermal annealing-induced vertical phase separation of copper phthalocyanine: Fullerene bulk heterojunction in organic photovoltaic cells. Appl. Phys. Lett. 2010, 97, 083302. [Google Scholar]
  49. Wei, H.X.; Li, J.; Cai, Y.; Xu, Z.Q.; Lee, S.T.; Li, Y.Q.; Tang, J.X. Electronic structures of planar and mixed C70/CuPc heterojunctions in organic photovoltaic devices. Org. Electron. 2011, 12, 1422–1428. [Google Scholar] [CrossRef]
  50. Grządziel, L.; Krzywiecki, M.; Peisert, H.; Chassé, T.; Szuber, J. Influence of ambient air exposure on surface chemistry and electronic properties of thin copper phthalocyanine sensing layers. Thin Solid Films 2011, 519, 2187–2192. [Google Scholar]
  • Sample Availability: Samples of the films are not available from the authors.

Share and Cite

MDPI and ACS Style

Van Dijken, J.G.; Brett, M.J. Dry Etching of Copper Phthalocyanine Thin Films: Effects on Morphology and Surface Stoichiometry. Molecules 2012, 17, 10119-10130. https://doi.org/10.3390/molecules170910119

AMA Style

Van Dijken JG, Brett MJ. Dry Etching of Copper Phthalocyanine Thin Films: Effects on Morphology and Surface Stoichiometry. Molecules. 2012; 17(9):10119-10130. https://doi.org/10.3390/molecules170910119

Chicago/Turabian Style

Van Dijken, Jaron G., and Michael J. Brett. 2012. "Dry Etching of Copper Phthalocyanine Thin Films: Effects on Morphology and Surface Stoichiometry" Molecules 17, no. 9: 10119-10130. https://doi.org/10.3390/molecules170910119

Article Metrics

Back to TopTop