Production of Stable Ion Beam of Os₃(CO)₁₂ with Compact Metal-Cluster-Complex Ion Source

Abstract

Metal-cluster-complex ion beams were produced stably using a cluster ion source, which is compact enough to be installed in commonly used secondary ion mass spectrometry (SIMS) systems. As a metal cluster complex, triosmium dodecacarbonyl, Os3(CO)12, was utilized, which has a molecular weight of 906.7. Since precise temperature control is necessary to sublimate the metal cluster complex stably without thermal decomposition, the ion source was equipped with compact heat-removal devices in addition to an external heater. Experimental results showed that the crucible temperature of the metal cluster complex can be maintained at about 130 °C in continuous operation, which is an appropriate temperature for sublimation without the problem of decomposition. The ion source produced steady-state beams of Os3(CO) n + (n=7 or 8) ions with a beam current exceeding 10 nA at 10 keV. Beam current increased with gas pressure, depending on the temperature of the crucible holding the metal cluster complex. The rate of the change in beam current was within a few percent per hour; hence, in view of stability, the ion source was confirmed as usable in SIMS. Furthermore, beam profile was investigated using a Faraday cup with a knife-edge as well as a GaAs/AlAs multilayer substrate as a beam target.

Cluster SIMS using metal cluster complex ions

“…Details of the metal cluster complex ion source have been reported previously [13,15]. In the present study, ion beams containing mainly Ir 4 (CO) 7 + ions are produced.…”

“…To demonstrate the concept, we have developed a new ion source using metal cluster complexes, subsequently demonstrating that stable metal cluster complex ion beams were produced [13]. As metal cluster complexes, triosmium dodecacarbonyl, Os 3 (CO) 12 , and tetrairidium dodecacarbonyl, Ir 4 (CO) 12 , have been utilized; they have molecular weights of 906.7 and 1104.9, respectively [14].…”

Time‐of‐Flight secondary ion mass spectrometry (TOF‐SIMS) using the metal‐cluster‐complex primary ion of Ir4(CO)7+

“…Details of the metal-cluster-complex ion source have been reported previously. [16,19] Briefly, it consists of a crucible holding the metal-cluster-complex, an electron-impact ionizer, an extractor, a Wien filter and an Einzel lens for focusing ion beams. By electron-impact ionization, fragment ions such as Ir 4 (CO) n + (n = 0-12) are formed; the most predominantly formed ions are Ir 4 (CO) 7 + .…”

Characteristics of a cluster‐ion beam of Os3(CO)n+ (n = 7 or 8) for low‐damage sputtering

“…Details of the experimental setup are described elsewhere. 18 Briefly, the ion source has a total length of about 70 cm, which is comparable in size to oxygen or cesium ion sources commonly used in SIMS. The cluster-ion source consists of a crucible holding the metal cluster complex, an ionizer, an extractor, a mass filter, and an Einzel lens for focusing ion beams.…”