Shape transition in very large germanium islands on Si(111)

Ge islands with areas up to hundreds of μm2 were grown on Si(111). These islands, grown above 750 °C and at a deposition rate of 1 monolayer/min, become decreasingly compact with increasing size and can have nonuniform cross sections with heights reaching over 500 nm. The largest islands are ramified, often comprising multiple discrete parts. X-rayphotoemission electron microscopy absorption maps show that the islands have a higher concentration of Ge at their centers, with more Si near the edges. We propose that the shape transformation is driven by strain relief at the island perimeters.

Patterned growth of nanoscale in clusters on the Si(111)-7×7 and Si(111)-Ge(5×5) reconstructions

Results of a study designed to investigate the possibility of using the Si(111)- Ge(5×5) surface reconstruction as a template for In cluster growth are described. As with Si(111)-7×7, the In adatoms preferentially adsorb in the faulted half-unit cell, but on Si(111)- Ge(5×5) a richer variety of cluster geometries are found. In addition to the clusters that occupy the faulted half-unit cell, clusters that span two and four half-unit cells are found. The latter have a triangular shape spanning one unfaulted and three, nearest neighbor, faulted half-unit cells, Triangular clusters in the opposite orientation were not found. Many of the faulted halfunit cells have a streaked appearance consistent with adatom mobility.

Modified Stranski–Krastanov growth in Ge/Si heterostructures via nanostenciled pulsed laser deposition

The combination of nanostenciling with pulsed laser deposition (PLD) provides a flexible, fast approach for patterning the growth of Ge on Si. Within each stencilled site, the morphological evolution of the Ge structures with deposition follows a modified Stranski–Krastanov (SK) growth mode. By systematically varying the PLD parameters (laser repetition rate and number of pulses) on two different substrate orientations (111 and 100), we have observed corresponding changes in growth morphology, strain and elemental composition using scanning electron microscopy, atomic force microscopy and μ-Raman spectroscopy. The growth behaviour is well predicted within a classical SK scheme, although the Si(100) growth exhibits significant relaxation and ripening with increasing coverage. Other novel aspects of the growth include the increased thickness of the wetting layer and the kinetic control of Si/Ge intermixing via the PLD repetition rate.

Indium clusters on the Ge (5× 5) wetting layer of Si (111)- 7× 7

The adsorption of In on the Si(111)−Ge(5×5) surface reconstruction has been studied with scanning tunneling microscopy and ab initio calculations to investigate the possibility of using this reconstruction as a template for cluster formation. As with In adsorption on Si(111)−7×7 at low substrate temperatures and low In fluences, the In adatoms are found to preferentially adsorb on the faulted half-unit cell. However, in contrast to In adsorption on Si(111)−7×7, the In adatoms are also frequently found in the unfaulted half-unit cell at low coverages. The filling of unfaulted unit cell halves is primarily due to the formation of large clusters that span multiple substrate half-unit cells. Moreover, many of the faulted half-unit cells have a streaked appearance that indicates that surface atoms within them are mobile.

Effect of spatial dispersion of the dielectric on the binding energy of D- ion in Si and Ge

Using a multivalley effective mass theory, we obtain the binding energy of a D- ion in Si and Ge taking into account the spatial variation of the host dielectric function. We find that on comparison with experimental results the effect of spatial dispersion is important in the estimation of binding energy for the D- formed by As in Si and Ge. The effect is less significant for the case of D- formed by P and Sb donors.

Subsurface deformation in dry sliding of hypo-eutectic Al-Si alloys

The subsurface deformation during dry sliding of Al-Si alloys is studied by fragmentation of silicon particles. The size of the fragmented particles does not vary with load. The depth of deformation is found to increase with increase in normal load. This experimental observation agrees with load-deformation depth characteristics obtained by a slip line field model.

Characterization of dry sliding wear of Al---Si alloys

Controversy exists in the published literature as to the effect of silicon content and pressure on the dry sliding wear of Al---Si alloys. The present paper attempts to clarify the question by reporting a statistical analysis of data obtained from factorially designed experiments conducted on a pinon-disc machine in the pressure range 0.105–1.733 MPa and speed range 0.19–0.94 m s−1. Under these conditions it was found that, in the range 4–24 wt.% Si, wear of binary unmodified alloys does not significantly differ between the alloys. However, it is significantly less than that corresponding to an alloy containing no silicon. The effect of pressure on wear rate was found to be linear and monotonie and, over the narrow range of speeds used, the wear rate was found to be unaffected by speed. The coefficient of friction was found to be insensitive to variations in silicon content, pressure and speed.

Die Großstadt als Gegner? : Zur Wahrnehmung Berlins in Literatur, Film und Hörspiel der späten Weimarer Republik

Tässä tutkielmassa tarkastellaan, miten Berliinin suurkaupunki vaikutti Weimarin tasavallan loppuaikoina yksilöön. Tutkimusaineistona on Alfred Döblinin romaani Berlin Alexanderplatz sekä Walter Ruttmannin elokuva Berlin. Die Sinfonie der Großstadt ja kuunnelma Weekend. Teoreettisena taustana hyödynnetään kulttuuri- ja mediahistorian mentaliteetti- ja sosiaalihistoriaa. Aihetta käsitellään myös historiallis-temaattisesta lähtökohdasta, eli työssä tutkitaan todellisen Berliinin asemaa kyseisenä aikana, modernin metropolin olemusta, modernin ajan murrosvaihetta sekä uusasiallisen taidesuuntauksen vaikutusta teoksiin. Weimarin tasavallan aikana Saksassa elettiin murroksen keskellä. Toisaalta yhteiskunta oli poliittisesti pirstoutunut ja taloudellisesti epävakaa, mutta toisaalta kulttuurielämä oli lyhyen aikaa rikasta. Suurkaupungin asukkailla oli enemmän vapaa-aikaa ja mahdollisuuksia toteuttaa itseään omassa ympäristössään. Toisaalta ajan ristiriitaisuus kuitenkin vaikeutti yksilöllisen elämäntavan toteutumista; ihmiset odottivat murroskauden päättymiseltä materiaalista tyydytystä, jolloin henkiselle kehitykselle jäi vähän tilaa. Tärkein kysymyksenasettelu koskee suurkaupungin roolia oman aikansa tuotteena: missä määrin kaupunki oli ihmisen todellinen vastustaja ja missä määrin sen asema oli kuviteltua? Todellisen Berliinin suhdetta reflektoidaan fiktiiviseen suurkaupunkiympäristöön. Ensin tarkastellaan Berliiniä toimijana murroskaudella ja sitten käsitellään ajan ja tilan havainnointia. Koska teokset ovat fiktiivisiä, erityisen tarkastelun kohteena on todellisuuden, fiktion ja simulaation suhde. Tässä yhteydessä tarkastellaan myös kaupungin ja maaseudun välistä problematiikkaa. Kolmannessa osassa esille nousee yksilön ja massan välinen suhde, joka sekin vaikuttaa ihmisen ja suurkaupungin väliseen vastakkainasetteluun. Ilmensikö koneiden ja liikenteen dominoiva asema futuristista asetelmaa? Lisäksi käsitellään alamaailman ja kultaisen 20-luvun välistä kuilua. Kaikkia kolmea teosta yhdistää 24 tunnin aikakäsite; ajalla on selkeästi rajattu alku ja loppu, ja myös tilan käsite on tarkastelussa tärkeä. Kaikissa teoksissa on hyödynnetty montaasitekniikkaa. Kohtaukset vaihtuvat hyvinkin nopeasti, jolloin lukija, katsoja tai kuulija vieraantuu varsinaisesta kohteestaan. Montaasi vaikuttaa ratkaisevasti myös kaupungin ja yksilön suhteen kuvaukseen. Suurkaupungista muotoutuu lähes hirviömäinen, personifioitu subjekti, joka konemaisella olemuksellaan pyrkii nujertamaan pienen ihmisen. Döblinin romaanissa kertoja toimii ikään kuin yksilöä vastaan liittämällä kerronnan väliin uutisaiheita, säätiedotuksia ja kohtalokertomuksia. Elokuvassa ja kuunnelmassa teknologisen kehityksen ihannointi on noussut etualalle: ihmiset muistuttavat sekä yksilöinä että massana koneita, jotka liikkuvat hektisen mekaanisesti eteenpäin kuin liikennevälineet. He eivät kyseenalaista ympäristöään eivätkä koe olevansa oravanpyörässä. Romaanin päähenkilö on heijastanut omat pelkonsa konkreettisesti suurkaupungin infrastruktuuriin, kerrostaloihin, jotka tuntuvat kaatuvan hänen päälleen. Yksilöllinen kehitys on vaarassa pysähtyä, sillä koneistuminen tekee yksilöistä massaa. Elokuvassa ja kuunnelmassa kamppailu suurkaupunkiorganismin ja ihmisten välillä jatkuu, mutta romaanissa kamppailu päättyy päähenkilön parantumiseen. Hänestä tulee mallikansalainen - vaiennettu ja kuuliainen. Kaikkien kolmen teoksen hahmoja kuvataan modernin ajan uhreina. Heiltä puuttuu mekanismi, jolla he voisivat käsitellä kokonaisuuksia. Modernin ajan hahmojen elämä on lopulta kuin tanssia tulivuoren päällä - epävarmaa ja riskialtista.

Scanning electron microscopy study of worn Al-Si alloy surfaces

A pin-on-disc machine was used to wear Al-Si alloy pins under dry conditions. Unmodified and modified binary alloys and commercial multi-component alloys were tested. The surfaces of the worn alloys were examined by scanning electron microscopy to identify distinct topographical features to aid elucidation of the mechanisms of wear.

Depth profile composition studies of thin film CdS: Cu,S solar cells using XPS and AES

Surface composition and depth profile studies of hemiplated thin film CdS:CuzS solar cells have been carried out using x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) techniques. These studies indicate that the junction is fairly diffused in the as-prepared cell. However, heat treatment of the cell at 210°C in air relatively sharpens the junction and improves the cell performance. Using the Cu(2p3p)/S(2p) ratio as well as the Cu(LVV)/(LMM) Auger intensity ratio, it can be inferred that the nominal valency of copper in the layers above the junction is Cut and it is essentially in the CUSS form. Copper signals are observed from layers deep down in the cell. These seem to appear mostly from the grain boundary region. From the observed concentration of Cd, Cu and S in these deeper layers and the Cu(LVV)/(LMM) ratio it appears that the signals from copper essentially originate partly from copper in CuS and partly from Cu2t trapped in the lattice. It is significant to note that the nominal valence state of copper changes rather abruptly from Cut to Cuz+ across the junction.

When film, fashion & interiors collide: Designing the After Darkly Graduate Fashion Show

In 2013 QUT Interior Design and Fashion Disciplines partnered to design the Catwalk for the QUT After Darkly Graduate Fashion Show. The ephemeral work (catwalk canopy and cinematic affects) was developed through collaboration between the authors based upon an undergraduate interior design unit ‘Filmic Interiors’ in which students were tasked with designing a fashion show. Filmic Interiors exploited the potential of film to influence, understand, and develop novel interior spaces through consideration of mise-en-scene, cinematic effects and atmospheric design strategies engaged by key film directors Jean Pierre Jeunet and Darren Aronofsky. The design outcome represents a hybridisation of student design proposals, contemplating both film and emerging collections from graduate fashion students. The work explored a number of iterations each testing material qualities and immaterial cinematic affects, as a means to develop new space. The process was led by experimentation undertaken by the designers through previous studio explorations surrounding the theme of ‘Strange Space’ and design practice ‘Making Strange’(Lindquist & Pytel, 2012). In doing so, the work paralleled the material formations of ‘obsessive collections’ and ‘making do’ evident in Jeunet’s scenography, rendering uncanny hybrid space (Ezra, 2008). Evocation of the immaterial found in much of director Aronofsky’s work, also became critical in the atmospheric experience intended for the show. This paper explores the process of collaboration and material experimentation in design, approached through a filmic lens. It provides insight into what happens when one enters into what can be termed an ‘ecology of production’, whereby the experimental making becomes the collaborative agent between designers, disciplines, and between stage and spectators. Finally it underlines the importance of ‘finding the work’ through material making and testing rather than through more controlled formalistic responses.

Trimming studies on polymer thick-film resistors

PVC-graphite polymer thick-film resistors were trimmed by a conventional air abrasive technique and the post-trim drift in resistance with time was found to be negative. The net decrease in resistance of trimmed resistors in a given time was found to be a function of resistor composition, cutting speed and temperature. Detailed studies showed this decrease to be due to a decrease in cut width with time. Two new methods, namely bombardment trimming and radiation trimming, were also tried for adjusting the resistance of these resistors and the results were compared with those obtained from abrasive trimming studies.