Study of Interfaces of Mo/Be Multilayer Mirrors Using X-ray Photoelectron Spectroscopy

Abstract

In the present work, formation of interfaces in the multilayer periodic Mo/Be mirror was studied using X-ray photoelectron spectroscopy. Chemical composition and significance of the interfaces depending on the number of periods were investigated by means of the XPS spectra decomposition technique. Formation of beryllide compounds at the interfaces was revealed. It was shown that two types of beryllide form at the interfaces depending on the film order: MoBe α , 4.0 < α < 5.0, at the Be-on-Mo (BOM) interface and MoBe β , 1.0 < β < 1.6, at the Mo-on-Be (MOB) interface. The increase in the number of periods from 1 to 3 leads to suppression of the MoBe α formation at the BOM interface, while quality of the MOB interface remains unchanged. In order to rationalize the observed phenomena, an assumption on the interface formation mechanism was made. According to this hypothesis, the chemical composition asymmetry of the interfaces arises from the difference in the diffusion mechanism of Be atoms: surface diffusion prevails during the MOB interface formation, while bulk diffusion is favorable during the BOM interface formation. In this regard, suppression of the beryllide formation at the BOM interface with increasing number of periods indicates reduction of bulk defects in the Mo film.

Effect of Insertion of B4C at the Interface Mo/Be Depending on the Film Order

“…In the current work, it is advisable to start from the formulation of the main conclusions on the Mo/Be multilayer established in our previous work. 7 We should also clarify the result obtained from the analysis of the Mo 3d spectrum. It is worth noting that the spectra, as shown in Figure 1, were measured at an ESCA module with an energy resolution of about 0.4 eV (in the previous work the measurements were carried out at ESCALab station providing energy resolution of 0.8 eV).…”

“…All XPS measurements were carried out at a 0°emission angle (normal to the surface). According to our previous work, 7 irradiation of the Mo/Be structure by photons with an energy of 1486.6 eV enables to collect information from a depth of 7−8 nm. To remove the surface oxide layer from the reference films, Ar + ion sputtering was applied using in situ the 1.5 keV ion beam at a 15°grazing incidence angle for 10 min prior to the measurements.…”

“…5,6 However, in reality, a significant decrease in the reflectance measured from a Mo/Be mirror is observed. As was shown in our earlier work, 7 the complexity of the problem is largely related to the formation of interlayers (beryllide compounds with different stoichiometry depending on the film order) at the interfaces of Mo and Be layers because of interdiffusion and chemical reactions during the synthesis of such system. The analysis revealed the increasingly important role of such interlayers.…”

Микроструктура Переходных Границ В Многослойных Мо/Ве-Системах

“…Остается не проясненным несоответствие выводов настоящей работы выводам работы [18], где утверждается, что соединение с большим количеством Ве образуется на границе Ве-на-Мо, а не наоборот. Данное несоответствие требует дополнительных исследований.…”

“…Единственной работой, затрагивающей вопрос структуры границ в многослойных структурах Mo/Be, является [18]. Здесь методами фотоэлектронной спектроскопии была исследована микроструктура переходных границ в системе Мо/Ве с разным количеством периодовот одного до ста.…”