Idiosyncrasies of Physical Vapor Deposition Processes from Various Knudsen Cells for Quinacridone Thin Film Growth on Silicon Dioxide

Abstract

Thin films of quinacridone deposited by physical vapor deposition on silicon dioxide were investigated by thermal desorption spectroscopy (TDS), mass spectrometry (MS), atomic force microscopy (AFM), specular and grazing incidence X-ray diffraction (XRD, GIXD), and Raman spectroscopy. Using a stainless steel Knudsen cell did not allow the preparation of a pure quinacridone film. TDS and MS unambiguously showed that in addition to quinacridone, desorbing at about 500 K (γ-peak), significant amounts of indigo desorbed at about 420 K (β-peak). The existence of these two species on the surface was verified by XRD, GIXD, and Raman spectroscopy. The latter spectroscopies revealed that additional species are contained in the films, not detected by TDS. In the film mainly composed of indigo a species was identified which we tentatively attribute to carbazole. The film consisting of mainly quinacridone contained in addition p-sexiphenyl. The reason for the various decomposition species effusing from the metal Knudsen cell is the comparably high sublimation temperature of the hydrogen bonded quinacridone. With special experimental methods and by using glass Knudsen-type cells we were able to prepare films which exclusively consist of molecules either corresponding to the β-peak or the γ-peak. These findings are of relevance for choosing the proper deposition techniques in the preparation of quinacridone films in the context of organic electronic devices.

Adsorption, desorption, and film formation of quinacridone and its thermal cracking product indigo on clean and carbon-covered silicon dioxide surfaces

“…A full mass spectrum of the molecules desorbing in the temperature range of the β-peak revealed that these molecules must be indigo. 7 In fact, the β-peak is very similar to desorption spectra obtained after deposition of pure indigo on SiO 2 . 10 At very low exposure (<3 Å), no desorption takes place at all.…”

“…Both masses belong to the mass spectrometer cracking pattern of QA. 7 While the γ-peak can clearly be attributed to the desorption of quinacridone, the β-peak cannot stem from QA since it does not show the cracking mass of 128 amu. A full mass spectrum of the molecules desorbing in the temperature range of the β-peak revealed that these molecules must be indigo.…”

“…A detailed analysis of QA evaporation from stainless steel and glass Knudsen cells, as well as of Langmuir evaporation, has been described in a previous paper. 7 As substrate material, silicon dioxide with a nominal thickness of 150 nm, thermally grown on 0.67 mm thick Si(001) wafers (Siegert Wafer), was used. The 1 × 1 cm 2 large substrates were mounted onto a stainless steel plate (via tantalum clamps), which could be cooled by LN 2 .…”

“…Electronic mail: a.winkler@tugraz.at that these particular molecules show a propensity to partial decomposition during sublimation. In a recent paper, 7 we described idiosyncrasies which we observed in PVD of QA by using various types of Knudsen cells (KCs). In both a quartz glass KC and a stainless steel KC at least one additional type of molecules, namely indigo (IN), emanated from the cells, in addition to QA.…”

Investigation of tattoo pigments by Raman spectroscopy

“…The spectrum of the heterocyclic quinacridone compound, PR122, had primary bands at 1645, 1593, and 1566 cm À1 , which agreed with previous studies. [42,43] Finally, the spectrum of PV23, the oxazine compound, had a distinct set of three intense bands (1425, 1384, and 1342 cm À1 ) as well as weaker bands that could be used to identify this pigment, as was also shown by Bell et al when identifying components in lilac paint samples. [44] Evaluation of pigment libraries Pigments from multiple manufacturers were evaluated to determine the robustness of the developed libraries.…”