X-ray Photoelectron Spectrometry Depth Profiling of Organic Thin Films Using C₆₀ Sputtering

Abstract

on CBP, were studied. In all cases, a clear multilayer structure was observed. The chemical composition and elemental state were preserved after C 60 + ion sputtering. The sputter rate was found to decrease with sputtering time. This is due to the deposition of amorphous carbon on the surface, with the rate of implantation highly dependent on the surface interacting with the ion beam.Owing to its high surface sensitivity, X-ray photoelectron spectroscopy (XPS, electron spectroscopy for chemical analysis) is one of the most common techniques for studying the outer surface of metals, semiconductors, ceramics, and polymers. There is often interest in not only the top atomic or molecular layers but also the depth distribution of elements in the region close to the surface. For this application, in situ ion sputtering is generally used.Argon sputtering is the most accepted technique for removing surface contaminants and obtaining information on the depth distribution of an element in a sample. However, this erosion technique is known to cause severe damage to organic samples 1 owing to preferential sputtering or sputter reduction. Hence, information on the chemical composition and the chemical state of elements is lost and argon sputtering cannot be used for depth profiling of polymer materials. Such damage is still observable at low (0.25 kV) beam energy 2 and with other ion species. 3Recently, buckminsterfullerene (C 60 ) ion guns were constructed by Ionoptika Ltd. 4,5 and were used to generate secondary ions for studying polymer surfaces. Molecular dynamics calculations suggested that C 60 + ions are more efficient in removing material 6 and leave behind a relatively thin damage layer. 7 The calculations also suggest that a C 60 + ion beam allows chemical imaging at higher sensitivity and better depth resolution. 8 Using C 60 as the primary ion in secondary ion mass spectroscopy (SIMS), organic materials including Irganox 1010, 9 PMMA, 10,11 barium arachidate, 12 and biological membranes 13 were studied. The results confirm that the sputter yield is increased and damage to the chemical structure is reduced. However, the composition of mixtures cannot be quantitatively analyzed with SIMS due to the nature of the ionization process. In order to gain more insights of composite systems, a direct quantifiable technique like XPS is desirable. Bulk polymers including PET 4 and PTFE 14 were also cleaned with a C 60 ion beam, and the chemical states of elements observed by XPS remained the same after the cleaning. In the present study, materials important for thin-film organic electronics, e.g., organic light-emitting diode (OLED) devices, were investigated by XPS using C 60 + sputtering. EXPERIMENTAL SECTIONXPS spectra were recorded on a PHI 5000 VersaProbe (ULVAC-PHI, Chigasaki, Japan) system using a microfocused (100 µm, 25 W) Al X-ray beam with a photoelectron takeoff angle of 45°. A dual-beam charge neutralizer (7-V Ar + and 30-V electron

Depth-profiling X-ray photoelectron spectroscopy (XPS) analysis of interlayer diffusion in polyelectrolyte multilayers

“…These stratified films were dried then analyzed using depth-profiling XPS paired with C 60 + sputtering to collect C1s, O1s, N1s, and Si2p high-resolution spectra. It is important to note that prolonged X-ray exposure and C 60 + sputtering may alter the chemical composition of PEMs and decrease the interface resolution (36,48). As described in Fig.…”

“…Many depth-profiling techniques use single-atom sputtering sources such as argon, applicable to inorganic materials but severely damaging to polymers (33)(34)(35). Only recently have cluster ion sources such as C 60 + been used in conjunction with XPS for analysis of polymer films with depth (33,36,37). Cluster ion C 60 + sputtering is much less damaging because the energy transfer from the ion to the material occurs primarily at the surface, minimizing the chemical damage deep into the film (38).…”

Surface-enhanced Raman scattering of C60 on co-modified substrate of Fe3O4 and Au nanoparticles

“…Au colloid was prepared through a redox process according to Frens's method [31], except that KAuCl 4 was substituted by HAuCl 4 . In 500 mL of deionized water, 0.2 mmol HAuCl 4 Á4H 2 O was dissolved and the solution was heated to boiling.…”

“…The investigations of fullerene materials have generated considerable interest because of their technological and scientific applications, especially in the form of thin films [1][2][3][4][5]. As the properties of fullerene thin films depend on interface configuration and adsorption patterns intimately, the study of the adsorption behavior, the charge transfer and the interaction between fullerene molecules and substrate are significant for the understanding of the film growth mechanisms and the determination of the optical and electronic properties of the fullerene films [6][7][8][9][10][11].…”

Physical Mechanisms of SiO$_{2}$ Target Sputtering with Accelerated Ions of C$_{60}$

“…Ионные пучки фуллерена C 60 нашли применение во вторичной ион-ной масс-спектрометрии (ВИМС) [1-4] для распыления анализиру-емого вещества, послойного анализа методом рентгеновской фото-электронной спектроскопии (РФЭС) [5,6], показана также возмож-ность формирования из них сверхтвёрдых нанокомпозитных по-крытий [7][8][9]. Интервал энергий, где происходит смена роста плён-ки на распыление поверхности, индивидуален для материала ми-шени [10] и, кроме того, может быть связан с химическим составом остаточной атмосферы вакуумной камеры [11].…”