Reaction Chemistry of Solid-State Pyridine Thin Films with Vapor Deposited Ag, Mg, and Al

Matz, Dallas L.; Pemberton, Jeanne E.

doi:10.1021/jp300795c

Cited by 8 publications

(23 citation statements)

References 80 publications

(169 reference statements)

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“…In fact, a-C is a common product as the result of reaction chemistry between aromatic systems and post-deposited Al and Ca. As has been shown in multiple cases in the previous work from this laboratory, a-C formation is usually initiated by aromatic ring reduction by these metals. ,,, …”

Section: Resultsmentioning

confidence: 55%

“…As has been shown in multiple cases in the previous work from this laboratory, a-C formation is usually initiated by aromatic ring reduction by these metals. 35,36,39,102 Additional new weak bands in the spectra from the α-6T/Ca system appear at 650, 950, 1150, and 2070 cm −1 . These are assigned to δ(C−H), ν(S−C−C−H), δ(S−CC−H), and ν(CC) modes, 103 respectively, which additionally confirms the occurrence of chemical reaction/degradation initiated by the deposited Ca.…”

Section: ■ Results and Discussionmentioning

confidence: 92%

“…The work function of bulk Mg (3.68 eV) is in between that for Ca (2.9 eV) and Al (4.2 eV), both of which were shown above to react by electron transfer with these thin α-6T films. Indeed, for all other organics studied to date in this laboratory, 37,39,40 Mg has reacted by electron transfer to the organic in a manner similar to Al and Ca. Thus, our expectation was that behavior with α-6T similar to that observed with Al and Ca would be observed.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…38 Also, thin-film, solid- state, small molecules used to model the building blocks of acceptor materials, namely, benzene and pyridine, react with the vapor-deposited metals Al, Mg, and Ca by accepting electrons to form radicals and/or dimers as well as graphitic carbon. 39,40 Similarly, Sang et al described reaction chemistry of α-terthiophene (α-3T) with Al and Ca in which electron transfer from these metals led to the formation of either amorphous carbon (a-C) or ring-opening reactions. 41 Similar studies have provided evidence for reaction chemistry of some sort between deposited LWFM and organics based on results from a wide array of techniques.…”

Section: ■ Introductionmentioning

confidence: 99%

“…C 60 anion radicals are observed due to Al-to-C 60 electron transfer leading to the degradation of C 60 and the formation of graphitic carbon . Also, thin-film, solid-state, small molecules used to model the building blocks of acceptor materials, namely, benzene and pyridine, react with the vapor-deposited metals Al, Mg, and Ca by accepting electrons to form radicals and/or dimers as well as graphitic carbon. , Similarly, Sang et al described reaction chemistry of α-terthiophene (α-3T) with Al and Ca in which electron transfer from these metals led to the formation of either amorphous carbon (a-C) or ring-opening reactions . Similar studies have provided evidence for reaction chemistry of some sort between deposited LWFM and organics based on results from a wide array of techniques. ,− In total, these studies indicate that interfacial energetics cannot be assumed based on the energy levels of the bulk materials alone, and electron transfer from LWFMs to any organic film is possible.…”

Section: Introductionmentioning

confidence: 99%

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Chemistry at the Interface of α-Sexithiophene and Vapor-Deposited Ag, Al, Mg, and Ca: A Molecular View

Sang

Pemberton

2019

J. Phys. Chem. C

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Interfacial chemistry of thiophene-based polymers and oligomers in contact with low work function metals is of interest for organic electronic devices. Herein, interfacial reactions of the model thiophene-based oligomer, α-sexithiophene (α-6T), in ultrathin (5 ML) films with vapor-deposited Ag, Al, Mg, and Ca are investigated using surface Raman spectroscopy and X-ray photoelectron spectroscopy under ultrahigh vacuum conditions. Although typically considered an electron donor, results indicate that α-6T is reduced by Al and Ca. The reduction product with Al is the tetrahydrothiophene, whereas complete degradation of the thiophene cores occurs with Ca with the formation of calcium sulfide. In contrast, for the higher work function Ag, contact doping from α-6T to Ag nanoparticles is observed, inducing the formation of polaron states at the interface. Inter-ring torsion by the C–C bond rotation is also induced by electron sharing between α-6T and Ag. Mg, which is expected to undergo electron transfer in a manner similar to Ca based on the work function, instead diffuses through these 5 ML films and deposits on or alloys with the Ag substrate beneath; however, electron transfer from Mg to α-6T is observed in thicker α-6T films suggesting that nucleation into structures with electronic characteristics that resemble those of bulk Mg metal occurs. Overall, the evolution of α-6T interfaces with these low work function metals alters the interfacial energetics through the formation of “gap” states, which ultimately impact the device performance.

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Section: Resultsmentioning

confidence: 55%

Section: ■ Results and Discussionmentioning

confidence: 92%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Chemistry at the Interface of α-Sexithiophene and Vapor-Deposited Ag, Al, Mg, and Ca: A Molecular View

Sang

Pemberton

2019

J. Phys. Chem. C

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High-Sensitivity Raman Spectrometer To Study Pristine and Irradiated Interstellar Ice Analogs

et al. 2013

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We discuss the novel design of a sensitive, normal-Raman spectrometer interfaced to an ultra-high vacuum chamber (5 × 10(-11) Torr) utilized to investigate the interaction of ionizing radiation with low temperature ices relevant to the solar system and interstellar medium. The design is based on a pulsed Nd:YAG laser which takes advantage of gating techniques to isolate the scattered Raman signal from the competing fluorescence signal. The setup incorporates innovations to achieve maximum sensitivity without detectable heating of the sample. Thin films of carbon dioxide (CO2) ices of 10 to 396 nm thickness were prepared and characterized using both Fourier transform infrared (FT-IR) spectroscopy and HeNe interference techniques. The ν+ and ν- Fermi resonance bands of CO2 ices were observed by Raman spectroscopy at 1385 and 1278 cm(-1), respectively, and the band areas showed a linear dependence on ice thickness. Preliminary irradiation experiments are conducted on a 450 nm thick sample of CO2 ice using energetic electrons. Both carbon monoxide (CO) and the infrared inactive molecular oxygen (O2) products are readily detected from their characteristic Raman bands at 2145 and 1545 cm(-1), respectively. Detection limits of 4 ± 3 and 6 ± 4 monolayers of CO and O2 were derived, demonstrating the unique power to detect newly formed molecules in irradiated ices in situ. The setup is universally applicable to the detection of low-abundance species, since no Raman signal enhancement is required, demonstrating Raman spectroscopy as a reliable alternative, or complement, to FT-IR spectroscopy in space science applications.

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Penetration and Reaction Depths of Vapor Deposited Ag, Mg, Al, and Ca on Oligothiophene Thin Films

Sang

Pemberton

2019

Chem. Mater.

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Physical vapor deposition of metal contacts onto thin film organic functional materials is widely used in organic electronic technologies. Using the oligothiophenes (OTs) α-sexithiophene (α-6T) and 2,2′:5′2″-terthiophene (3T) as models for thiophene-containing functional organic films, the metal/organic interface chemistry, metal penetration and reaction depths, and surface metallization processes are investigated and compared for Ag, Al, Mg, and Ca contacts using Raman and X-ray photoelectron spectroscopies. Ag shows only modest penetration, with some surface metallization but no reaction chemistry on OTs. Al and Ca induce some OTs reaction but exhibit the least propensity to penetrate these films with the greatest ability to metallize on the surface. In contrast, Mg exhibits complete penetration of 5 ML OT films with no reaction chemistry or surface metallization. On 50 ML OT films, however, Mg still exhibits the greatest depth of penetration with no surface metallization but does induce a small amount of reaction chemistry initiated by electron transfer from Mg to the OT film. These results reveal significant differences in the depth to which the deposited metal chemically impacts OT thin films during physical vapor deposition and reinforce the critical role of interface chemistry on the performance of organic electronic devices formed with such materials.

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Reaction Chemistry of Solid-State Pyridine Thin Films with Vapor Deposited Ag, Mg, and Al

Cited by 8 publications

References 80 publications

Chemistry at the Interface of α-Sexithiophene and Vapor-Deposited Ag, Al, Mg, and Ca: A Molecular View

Chemistry at the Interface of α-Sexithiophene and Vapor-Deposited Ag, Al, Mg, and Ca: A Molecular View

High-Sensitivity Raman Spectrometer To Study Pristine and Irradiated Interstellar Ice Analogs

Penetration and Reaction Depths of Vapor Deposited Ag, Mg, Al, and Ca on Oligothiophene Thin Films

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