Focused ion beam creation and templating of InAs and InAs/InP nanospikes

Ion beam irradiation has been examined as a method for creating nanoscale semiconductor pillar and cone structures, but has the drawback of inaccurate nanostructure placement. We report on a method for creating and templating nanoscale InAs spikes by focused ion beam (FIB) irradiation of both homoepitaxial InAs films and heteroepitaxial InAs on InP substrates. These 'nanospikes' are created as In droplets, formed due to FIB irradiation, act as etch masks for the underlying InAs. By pre-patterning the InAs to influence In droplet movement, nanospike locations on homoepitaxial InAs may be controlled with limited accuracy. Creating nanospikes using an InAs/InP heterostructure provides an additional measure of control over where the spikes form because nanospikes will not form on exposed regions of InP. This effect may be exploited to accurately control nanospike placement by pre-patterning an InAs/InP heterostructure to control the location of the InAs/InP interface. Using this heterostructure templating method it is possible to accurately place nanospikes into regular arrays that may be useful for a variety of applications.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90790/1/0957-4484_22_35_355302.pd

Recent Improvements to the Acoustical Testing Laboratory at the NASA Glenn Research Center

The Acoustical Testing Laboratory (ATL) consists of a 27 by 23 by 20 ft (height) convertible hemi/anechoic chamber and separate sound-attenuating test support enclosure. Absorptive fiberglass wedges in the test chamber provide an anechoic environment down to 100 Hz. A spring-isolated floor system affords vibration isolation above 3 Hz. These specifications, along with very low design background levels, enable the acquisition of accurate and repeatable acoustical measurements on test articles that produce very low sound pressures. Removable floor wedges allow the test chamber to operate in either a hemi-anechoic or anechoic configuration, depending on the size of the test article and the specific test being conducted. The test support enclosure functions as a control room during normal operations. Recently improvements were accomplished in support of continued usage of the ATL by NASA programs including an analysis of the ultra-sonic characteristics. A 3 dimensional traverse system inside the chamber was utilized for acquiring acoustic data for these tests. The traverse system drives a linear array of 13, 1/4"-microphones spaced 3" apart (36" span). An updated data acquisition system was also incorporated into the facility

Lateral composition modulation in AlAs/InAs and GaAs/InAs short period superlattices structures: The role of surface segregation

The effect of In surface segregation on the microstructure of short period superlattices (SPSs) in two different material systems with nominally equivalent lattice misfit, AlAs/InAs and GaAs/InAs, has been investigated and compared. It was found that the quality of the SPSs and the appearance of lateral composition modulation are remarkably different in these two systems. For AlAs/InAs SPSs grown at temperatures of T=500 °C,T=500 °C, uniform structures devoid of lateral composition modulation were obtained. Samples grown at T>500 °CT>500 °C exhibit lateral composition modulation. Uniform and homogeneous SPS structures were not obtained in the GaAs/InAs structures over the entire temperature range examined in this study (475 °C⩽T⩽510 °C).(475 °C⩽T⩽510 °C). Instead, lateral composition modulation with varying degrees of regularity was always observed. It was found that In segregation and roughening determine the microstructure. A kinetic exchange model predicts that at an optimum temperature the SPS layers are more intermixed for the AlAs/InAs SPSs. Thus, the lattice mismatch is lower and the driving force for roughening is reduced, resulting in uniform SPS structures. Growing the structure away from the optimum temperature for smooth growth may induce roughening-driven composition modulation. The GaAs/InAs structures are less intermixed over the temperatures studied, which results in higher mismatch between the individual layers and a higher driving force for roughening and lateral composition modulation. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69963/2/JAPIAU-91-1-237-1.pd

Prisutnost inhibitornih tvari u sirovom mlijeku na području Crne Gore

The Dairy Laboratory at Biotechnical Faculty in Podgorica tested using microbiological inhibitor test - Delvotest®Accelerator, presence of inhibitory substances in raw milk produced on dairy farms of individual producers, cooperates of Montenegrian dairies. During period of six months, 6161 samples of raw milk were tested and it was determined that 478 samples or 7.84 % were positive. This is a significantly higher percentage of positive samples in comparison to European Union countries, but it is not surprising, considering that in these countries there is a decades-old regular system for antibiotic residues control in milk, while in Montenegro testing is provided on level of annual monitoring. The results of analysis indicate that in Montenegro, it is necessary to introduce regular systematic control of residues of antibiotics and other inhibitory substances in raw milk.Laboratorij za mljekarstvo Biotehničkog fakulteta iz Podgorice korištenjem mikrobiološkog inhibitor testa - Delvotest Accelerator, testirao je prisustvo inhibitornih tvari u sirovom mlijeku proizvedenom na farmama individualnih proizvođača, kooperanata mljekara u Crnoj Gori. Tijekom šestomjesečnog razdoblja testiran je 6161 uzorak sirovog mlijeka, a pritom je utvrđeno kako je 478 ili 7,84 % uzoraka bilo pozitivno. U usporedbi sa zemljama Europske Unije, ovo je značajno veći postotak pozitivnih uzoraka, što ne iznenađuje obzirom na to da u zemljama EU-a već desetljećima postoji redoviti sustav za kontrolu rezidua u mlijeku, dok se testiranje u Crnoj Gori provodi na razini godišnjeg monitoringa. Rezultati analiza upozoravaju da je u Crnoj Gori nužno uvesti redoviti sustavni nadzor rezidua antibiotika i drugih inhibitornih tvari u sirovom mlijeku

Lateral composition modulation in mixed anion multilayers

Lateral composition modulation on the group V sublattice has been observed in GaAs/GaSb short period superlattices. Cross sectional transmission electron microscopy and x-ray diffraction reciprocal space maps reveal that all structures are phase-separated with Sb compositions for the strongest modulated structure of x = 0.73x=0.73 in the Sb-rich regions, x = 0.55x=0.55 in the As-rich regions, and wavelengths 15 ⩽ Λ ⩽ 20 nm.15⩽Λ⩽20nm. The composition modulation observed in these films is not due to spinodal decomposition, because an alloy grown at the same conditions results in a homogeneous layer, but may be related to vertical stacking of quantum dots that nucleate during the growth of the structure. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69861/2/APPLAB-81-18-3368-1.pd

To nie jest książka romantyczna. Jacek Filek, Życie, etyka, inni. Scherza i eseje filozoficzne, Wydawnictwo Homini, Kraków 2010, s. 351.

Zeszyty Naukowe TDU

The Impact of The Initial Surface Reconstruction on Heteroepitaxial Film Growth and Defect Formation

While it is well known that growth conditions such as temperature greatly affect defect incorporation in thin films, less is known about the direct effects of the surface reconstruction. In this work, we examine the effect of the initial surface reconstruction on defect incorporation in GaSb/GaAs(001) lattice mismatched films. The stress built up in GaSb films grown on As-terminated and Sb-terminated GaAs was monitored during film growth and shows that the total relaxation is similar in both films along the [110], but lower on the Sb-terminated surface along the . These differences can be understood by examining the ability for the two surface terminations to accommodate strain. The resulting films show that the density of 3D islands is lower for the Sb-terminated surfaces, and that lattice mismatch strain is further accommodated by a 5° tilt. In contrast, the As-terminated surface contains both stacking faults and misfit dislocations. These results demonstrate the possibility to engineer specific defects into films by controlling the starting surface of film growth

Cooperative nucleation leading to ripple formation in InGaAs/GaAs films

In0.25Ga0.75AsIn0.25Ga0.75As epilayers were grown on GaAs (001) substrates (1.8% misfit strain) by molecular beam epitaxy to investigate the two-dimensional to three-dimensional transition as a function of thickness (t ⩽ 30 MLs).(t⩽30MLs). Tapping-mode atomic force micrographs show the evolution of the morphology as a function of thickness. As the film is deposited, the nucleation of 3D islands followed by cooperative nucleation of pits is observed. As the thickness increases, both islands and pits continue to nucleate and grow until they coalesce, resulting in a fully formed ripple morphology running along the [10].[11̄0]. The ripples also exhibit a secondary alignment roughly along the 〈310〉 which is attributed to the nucleation of islands with {136} faces. © 2000 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70708/2/APPLAB-76-17-2382-1.pd