Friction and Wear Characteristics of C/Si Bi-layer Coatings Deposited on Silicon Substrate by DC Magnetron Sputtering

The tribological behavior of carbon/silicon bi-layer coatings deposited on a silicon substrate by DC magnetron sputtering was assessed and compared to that of amorphous carbon and silicon coatings. The motivation was to develop a wear resistant coating for silicon using thin layers of amorphous carbon and silicon. Wear tests were conducted by sliding a stainless steel ball against the coating specimens under applied normal loads in the range of 20 * 50 mN. Results showed that the wear rate of the bi-layer coating was strongly dependent on the ratio of thickness between the carbon and silicon layers. The wear rate of the bi-layer coating with 25 nm thick carbon and 102 nm thick silicon layers was about 48 and 20 times lower than that of the single-layer amorphous carbon and amorphous silicon coating, respectively. In addition, the steady-state friction coefficient of the bi-layer coating could be decreased to 0.09 by optimizing the thickness of the layer. Finally, a model for the wear reduction mechanism of the carbon/silicon bi-layer coating was proposed

Effect of working gas pressure on interlayer mixing in magnetron-deposited Mo/Si multilayers

By methods of cross-sectional transmission electron microscopy and small-angle x-ray scattering (λ = 0.154 nm) the influence of Ar gas pressure (1 to 4 mTorr) on the growth of amorphous interfaces in Mo/Si multilayers (MLs) deposited by DC magnetron sputtering is studied. The significant reduction in the ML period, which is evident as a volumetric contraction, is observed in MLs deposited at Ar pressure where the mean-free path for the sputtered atoms is comparable with the magnetronsubstrate distance. Some reduction in the thickness of the amorphous interlayers with Ar pressure increase is found, where the composition of the interlayers is enriched with molybdenum. The interface modification resulted in an increase in EUV reflectance of the Mo/Si ML

СТРУКТУРА И ФАЗОВЫЙ СОСТАВ МНОГОСЛОЙНЫХ РЕНТГЕНОВСКИХ ЗЕРКАЛ W-Si

Методами рентгеновской дифрактометрии в жесткой области (l~0,154 нм) исследована фазовая структура, состав и строение многослойных рентгеновских зеркал (МРЗ) W/Si с толщиной слоев вольфрама tW2,7 нм слои вольфрама имеют поликристаллическую (ОЦК) структуру, а при tW<1,9 нм они аморфны. При помощи sin2Y-метода установлено, что в тонких кристаллических слоях вольфрама (tW<10 нм) может содержаться более 3 ат.% Si. Растягивающие напряжения в слоях кристаллического вольфрама не превышают 1,1 ГПа. Построение функций радиального распределения атомов позволило установить, что аморфные слои вольфрама имеют расположение атомов, близкое к b-W. Во всех образцах за счет взаимодействия на межфазных границах наблюдается формирование силицидных прослоек, в результате чего реальная толщина слоев вольфрама меньше номинальной. Аморфные силицидные прослойки, обязательно формирующиеся на стадии изготовления МРЗ, содержат дисилицид вольфрама. В зависимости от скорости осаждения дисилицид может иметь расположение атомов, близкое либо к тетрагональной фазе, t-WSi2 (~0,6 нм/с.), либо к гексагональной фазе, h-WSi2 (~0,15 нм/с.). Представлена уточненная модель строения аморфных МРЗ W/Si. Предложены механизмы формирования силицидных прослоек, согласно которым нижние силицидные прослойки (W-на-Si) формируются преимущественно за счет баллистического перемешивания атомов вольфрама и кремния, а верхние – вследствие диффузионного перемешивания. Сделана оценка коэффициентов взаимной диффузии, которые позволили установить, что осаждаемая поверхность слоев может быть разогрета, по меньшей мере, на 250° выше температуры подложки. Предложены пути снижения межфазного взаимодействия

Single shot extreme ultraviolet laser imaging of nanostructures with wavelength resolution

We have demonstrated near-wavelength resolution microscopy in the extreme ultraviolet. Images of 50 nm diameter nanotubes were obtained with a single {approx}1 ns duration pulse from a desk-top size 46.9 nm laser. We measured the modulation transfer function of the microscope for three different numerical aperture zone plate objectives, demonstrating that 54 nm half-period structures can be resolved. The combination of near-wavelength spatial resolution and high temporal resolution opens myriad opportunities in imaging, such as the ability to directly investigate dynamics of nanoscale structures

Interdiffusion in Sc/Si multilayers

An understanding of interdiffusion in nano-scale multilayers is of great scientific and practical interest because intermixing is responsible for temporal and thermal instability of EUV and soft X-ray multilayer mirrors. In this paper we study the kinetics of silicide growth in Sc/Si layered coatings. It was found that an amorphous ScSi silicide forms at the scandium-silicon interface. The growth of the ScSi silicide layer obeys diffusion kinetics rather than a chemical reaction kinetics. The silicide growth is limited by the diffusion of Si atoms through the silicide layer towards the silicide-scandium interface where the chemical reaction takes place. As a result of a large asymmetry of interdiffusion the growth of the silicide occurs mainly at the silicide-scandium interface. The diffusion growth of the silicide deviates significantly from the classic parabolic law at the early stage of interdiffusion (Fig. 1). Such a nonlinear growth behavior can be explained with a relaxation model. The growth rate is maximal in the beginning of annealing due to a large amount of excess free volume in the as-deposited multilayer. During the annealing a relaxation processes occurs, and diffusion slows down. Eventually the growth rate is stabilized, and a parabolic regime of the silicide growth is observed