Effect of SIMS ionization probability on depth resolution for organic/inorganic interfaces

Abstract

Secondary ion mass spectrometry (SIMS) relies on the fact that surface particles ejected from a solid surface are ionized under ion bombardment. By comparing the signal of molecular secondary ions desorbed from an organic film with that of the corresponding sputtered neutral precursor molecules, we investigate the variation of the molecular ionization probability when depth profiling through the film to the substrate interface. As a result, we find notable variations of the ionization probability both at the original surface and in the interface region, leading to a strong distortion of the measured SIMS depth profile. The experiments show that the effect can act in two ways, leading either to an apparent broadening or to an artificial sharpening of the observed film-substrate transition. As a consequence, we conclude that care must be taken when assessing interface location, width, or depth resolution from a molecular SIMS depth profile.

ToF-SIMS Depth Profiling of Metal, Metal Oxide, and Alloy Multilayers in Atmospheres of H2, C2H2, CO, and O2

“… 52 − 54 Since the particles are ionized in the plume, there is no matrix around them to affect the ionization. 53 Laser-SNMS can be used in depth profiling, 55 thereby improving the ionization yield. 56 , 57 With this method, we can selectively ionize only some of the neutral particles (resonant laser-SNMS) 58 or nonselectively ionize all of them (nonresonant).…”

“…One commonly applied approach is laser postionization of the neutral sputtered particles (laser-SNMS). − Since the particles are ionized in the plume, there is no matrix around them to affect the ionization . Laser-SNMS can be used in depth profiling, thereby improving the ionization yield. , With this method, we can selectively ionize only some of the neutral particles (resonant laser-SNMS) or nonselectively ionize all of them (nonresonant) . In the case of resonant laser-SNMS, we must know exactly what is being analyzed, and in the case of the nonresonant approach, we must make sure that the laser intensity is high enough to ionize all the particles .…”

Новый Подход К Анализу Фазового Состава Углеродсодержащих Материалов Методом Времяпролетной Вторично-Ионной Масс-Спектрометрии

“…Наиболее принципиальной является новая возможность послойного молекулярного анализа, объединившего статический и динамический режимы ВИМС [1]. Такой анализ становится все более востребованным для изучения полупроводниковых и диэлектрических органических материалов и биологических объектов [2][3][4]. Наряду с анализом молекулярных структур в работах [5,6] изучалась возможность фазового анализа методом ВИМС углеродсодержащих материалов, таких как алмаз, алмазоподобный углерод (DLC) и графит.…”