Self-assembled germanium nanostructures formed using electron-beam annealing

D.A. Carder,A. Markwitz,H. Baumann,J. Kennedy 한국물리학회 2008 Current Applied Physics Vol.8 No.3,4

Germanium nanostructures have been fabricated on silicon substrates using ion-beam sputtering growth followed by an exsitu annealing step. The substrates are not heated during growth, resulting in a post-growth deposited layer ~225 nm thick with a surface which has no evidence of nanostructure formation. Following annealing at temperatures of 400–700℃ dramatic nanostructuring isobserved at the surface. For temperatures below 600℃ atomic force microscopy analysis reveals dense arrays of nanostructures withheights typically around 5-30 nm. Increased feature size and surface roughening is observed for samples annealed above 600℃, witha broadened size distribution centred at 450 nm. This is assigned to intermixing at the Si/Ge interface, which reduces the stress in thelayer, allowing larger features to form.

Optimised process for fabricating functional silicon nanowhisker arrays

A. Markwitz,M. Rudolphi,B. Barry,H. Baumann 한국물리학회 2008 Current Applied Physics Vol.8 No.3,4

Silicon nanostructures, called silicon nanowhiskers, are grown by electron beam annealing of wafer silicon. It is desirable to be able tocontrol sizes and locations of arrays of silicon nanowhiskers for eld emission applications. Nitrogen, oxygen and silicon ions wereimplanted at 1524 keV with uences ranging from 1012 to 1015 ions cm. 2 whisker growth in specied regions and to search for the minimum level of implanted ions necessary to suppress silicon nanowhiskergrowth. Particularly interesting results were obtained for the nitrogen ion implantation series where total suppression is achieved byimplanting 5 · 1014 N+ cm. 2. However, implanting 1· 1014 N+ cm. 2 results in an increase in nanowhisker density of a factor of threecoupled with a decrease in nanowhisker height by a factor of two. Silicon was also found to suppress silicon nanowhisker growth suc-cessfully; however oxygen implantations resulted in a decrease of nanowhisker growth with increasing uence but suppression of nano-whisker growth at 1· 1015 O+ cm. 2 nanowhisker growth area by low-energy nitrogen and silicon ion implantation.

Field emission properties of self-assembled silicon nanostructures formed by electron beam annealing

S. Johnson,A. Markwitz,M. Rudolphi,H. Baumann,S.P. Oei,K.B.K. Teo,W.I. Milne 한국물리학회 2006 Current Applied Physics Vol.6 No.3

Arrays of silicon nanostructures on n- and p-type silicon (100) substrates were fabricated using electron beam annealing of untreated silicon at 1100 C. Following annealing for 15 s, the nanostructures exhibit an average height of 8 ± 1 nm and a surface density of 11 lm2, independent of the substrate conduction type. Following annealing for 600 s the individual nanostructures coalesce and the surface appears roughened with an rms roughness of 30 nm. The field emission properties of these nanostructure arrays have been assessed and electron emission through Fowler–Nordheim tunnelling was confirmed. The difference in threshold field for electron emission from the nanostructured and roughened substrates is related to the geometrical differences between the substrate surfaces. At large electric fields, space charge limited conduction dominates the field emission characteristics of the nanostructured surface.

Plasma immersion nitrogen implantation into silicon and rapid thermal electron beam annealing for surface structuring

A. Markwitz,V. J. Kennedy,K. Short,M. Rudolphi,H. Baumann 한국물리학회 2004 Current Applied Physics Vol.4 No.2-4

(100) and (111) silicon substrates were implanted with 10 keV Nþ2 ions using plasma immersion ion implantation (PI3). Series ofspecimens were implanted in the uence range from 0.5 to 1.6· 1016 cm. 2 and subsequently annealed at 1000.C (radiation tem-perature) for 60 s with a raster scanned electron beam (EB-RTA) to investigate surface structuring after EB-RTA. Atomic forcemicroscopy (AFM) revealed that the combination of PI3 and EB-RTA resulted in a roughening of the surface on the lower 100 nmscale depending on the nitrogen uence used in the experiments. Similar ion implantation and annealing protocols using an ac-celerator based system in conjunction with EB-RTA showed, however, smooth surfaces on the 3 nm scale. Selected results arepresented providing evidence for the possibility of controlling the surface structuring of implanted surfaces via PI3 process para-meters.

Formation of large SiC nanocrystals on Si(1 0 0) by 12C implantation and electron beam annealing

A. Markwitz,S. Johnson,J. Kennedy,M. Rudolphi,H. Baumann 한국물리학회 2006 Current Applied Physics Vol.6 No.3

Scanning electron microscopy and nuclear reaction analysis have been used to study annealing eects of 10 keV12C implanted andelectron beam annealed silicon (10) substrates that cause the formation of large SiC nanocrystals named nanoboulderson silicon.Wafer silicon was implanted with varying uences from 0.38 to 1.14· 1017 atoms cm. 2 and subsequently annealed at 1000.C for15 s. The deuterium induced12C(d,p)13C reaction was used to measure the12C dose quantitatively. It was found that the implanted car-bon remained in the specimen after annealing. This result, coupled with geometrical analyses of the resulting nanostructures suggest thatfollowing nucleation, the SiC nanocrystals grow as a result of C and Si diusion across the substrate surface, that became oxide freeduring annealing under vacuum conditions.

The 8th International Comparison of Absolute Gravimeters 2009: the first Key Comparison (CCM.G-K1) in the field of absolute gravimetry

Jiang, Z,Pá,linká,š,, V,Arias, F E,Liard, J,Merlet, S,Wilmes, H,Vitushkin, L,Robertsson, L,Tisserand, L,Pereira Dos Santos, F,Bodart, Q,Falk, R,Baumann, H,Mizushima, S,Mä,kinen, J Springer-Verlag 2012 METROLOGIA -BERLIN- Vol.49 No.6

<P>The 8th International Comparison of Absolute Gravimeters (ICAG2009) took place at the headquarters of the International Bureau of Weights and Measures (BIPM) from September to October 2009. It was the first ICAG organized as a key comparison in the framework of the CIPM Mutual Recognition Arrangement of the International Committee for Weights and Measures (CIPM MRA) (CIPM 1999). ICAG2009 was composed of a Key Comparison (KC) as defined by the CIPM MRA, organized by the Consultative Committee for Mass and Related Quantities (CCM) and designated as CCM.G-K1. Participating gravimeters and their operators came from national metrology institutes (NMIs) or their designated institutes (DIs) as defined by the CIPM MRA. A Pilot Study (PS) was run in parallel in order to include gravimeters and their operators from other institutes which, while not signatories of the CIPM MRA, nevertheless play important roles in international gravimetry measurements. The aim of the CIPM MRA is to have international acceptance of the measurement capabilities of the participating institutes in various fields of metrology. The results of CCM.G-K1 thus constitute an accurate and consistent gravity reference traceable to the SI (International System of Units), which can be used as the global basis for geodetic, geophysical and metrological observations of gravity. The measurements performed afterwards by the KC participants can be referred to the international metrological reference, i.e. they are SI-traceable.</P><P>The ICAG2009 was complemented by a number of associated measurements: the Relative Gravity Campaign (RGC2009), high-precision levelling and an accurate gravity survey in support of the BIPM watt balance project. The major measurements took place at the BIPM between July and October 2009. Altogether 24 institutes with 22 absolute gravimeters (one of the 22 AGs was ultimately withdrawn) and nine relative gravimeters participated in the ICAG/RGC campaign.</P><P>This paper is focused on the absolute gravity campaign. We review the history of the ICAGs and present the organization, data processing and the final results of the ICAG2009.</P><P>After almost thirty years of hosting eight successive ICAGs, the CIPM decided to transfer the responsibility for piloting the future ICAGs to NMIs, although maintaining a supervisory role through its Consultative Committee for Mass and Related Quantities.</P>