MBE

ABSTRAK ANALISIS PENGARUH TEGANGAN EKSTRAKSI TERHADAP DIAMETER SPOT BERKAS ELEKTRON MBE DI PSTA-BATAN DENGAN SIMULASI MENGGUNAKAN SOFTWARE SIMION 8.1. Mesin Berkas Elektron (MBE), telah banyak dikembangkan sebagai sumber radiasi pada proses iradiasi suatu produk industri. Di PSTA-BATAN telah dilakukan rancangbangun MBE dan untuk mencapai sesuai spesifikasi dilakukan pengembangan diantaranya dengan menambah tabung akselerator yang digunakan. Penambahan tabung akselerator akan mempengaruhi lintasan berkas elektron yang terjadi dan diameter spot berkas elektron pada window. Dengan demikian, diperlukan simulasi dengan tujuan untuk memprediksi lintasan berkas elektron yang terjadi dan ukuran diameter spot berkas elektron pada window. Simulasi dilakukan menggunakan software SIMION 8.1 dan didasarkan dari data-data geometri sumber elektron dengan elektroda Pierce, variasi tegangan ekstraksi dan tabung akselerator yang digunakan. Hasil smulasi menunjukkan bahwa makin besar tegangan ekstraksi maka makin besar energi berkas elektron keluar dari sumber elektron sehingga mempunyai kekakuan (rigidity) yang lebih tinggi dan tidah mudah dibelokkan. Akibatnya makin tinggi tegangan ekstraksi maka diameter spot berkas elektron sampai di window makin kecil. Diameter spot berkas elektron optimum diperoleh pada tegangan ekstraksi 10 kV dan 12 kV yaitu masing-masing d 1 = 5,41 ± 0,05 cm dan d 2 = 5,44 ± 0,05 cm. Kata kunci : lintasan dan spot berkas elektron, SIMION 8.1. ABSTRACT ANALISYS OF EXTRACTION VOLTAGE EFFECT ON ELECTRON BEAM SPOT DIAMETER OF EBM IN PSTA-BATAN WITH SIMULATION USING SOFTWARE SIMION 8.1. Electron Beam Machine (EBM), has been widely developed as a source of radiation in the irradiation process of an industrial product. In PSTA-BATAN has been designed and constructed of EBM and to achieve the required specifications an addition of accelerating tube has been added. The addition of an accelerating tube will influences the electron beam trajectory and the electron beam spot of diameter at the window. Therefore, a simulation required with the aim to predict the electron beam trajectory and the diameter of the beam spot.. Simulation was done using SIMION 8.1 software and based on geometry data of electron gun with Pierce electrode, an extraction voltage and accelerator tube were varied. The results show that the greater of extraction voltage, the greater the electron beam energy so that it has a higher rigidity and thisis not easily deflected. As a result, the higher the extraction voltage, the diameter of electron beam spot reaches the window is smaller. The optimum diameter of beam spot was achieved at the 10 kV and 12 kV of extraction voltages. At this condition the diameter is d 1 = 5.41 ± 0.05 cm and d 2 = 5.44 ± 0.05 cm respectively.

La medicina basada en evidencias (mbe) es un término que surge a principios de 1990; a partir de esta fecha ha tenido un gran impacto en el ámbito médico, por lo que es frecuente escuchar que se alude a la mbe para avalar los procedimientos o tratamientos que se les realizan a los enfermos. No obstante, existe confusión sobre su verdadero valor y la manera de utilizarla. En este documento se plantean respuestas a los diversos interrogantes que generan el uso e interpretación de la mbe.

This study aimed to evaluate the temporal change and accuracy of interpolation techniques used for spatial zonation of two groundwater quantity parameters including water table and depth to water table over 11 years. The study was conducted based on the data collected from piezometric wells of Sari-Neka Plain in Mazandaran Province, Iran. The investigated methods included a set of geostatistical approaches involving simple Kriging, ordinary Kriging, Radial Basis Function (RBF), and a deterministic interpolation method called Inverse Distance Weighting (IDW) with powers of 1 and 5. Subsequent to quality control and data normalization, the most appropriate variogram was chosen based on low RSS and high r 2 while the most suitable interpolation technique was determined regarding the cross validation, Mean Absolute Error (MAE), and Mean Bias Error (MBE). The results demonstrated that Simple Kriging was the most suitable method for zoning the depth to groundwater over the years 2001, 2006, and 2012. Meanwhile, the most suitable methods for zoning the water table included IDW with a power of 1for the year 2001, RBF for the year 2006, and IDW with a power of 5 for the year 2012. The important finding was that the interpolation methods showed a lower error for estimating water table than estimating depth to groundwater. This study also revealed a drop in water table in the study area over the 11 years' period. Meanwhile, new water table classes have been added and extended between the years 2006 and 2012 that had not existed five years earlier. The highest water table losses were observed in three points at 13m depth to water table in the middle and northern parts of the study area.

Photoluminescenceintensityenhancementhasbeenobservedforself-assembledInAsquantumdots
(QDs) coatedwithgoldnanoparticlesandassociatedtosurfaceplasmon(SP)couplingeffects.Thiseffect
wasinvestigatedfordifferenttemperatures,excitationenergy,laserpower,GaAscaplayerthickness,and
QD morphology.ItwasfoundthattheSP–QD couplingefficiency increaseswiththeincreaseofthe
temperature.ItwasalsoobservedthatthiseffectisenhancedforQDsgrownon(311)BGaAsoriented
substrates.

We report room-temperature Raman studies of strained (100) and (311)B GaAs1xBix epitaxial
layers for x0.039. The Raman spectra exhibit a two-mode behavior, as well as disorder-activated
GaAs-like phonons. The experimental results show that the GaAs-like LO(C) mode experiences a
strong composition-dependent redshift as a result of alloying. The peak frequency decreases
linearly from the value for pure GaAs (293 cm1) with the alloyed Bi fraction x and the
introduced in-plane lattice strain ek, by DxLO ¼ Dxalloy  Dxstrain. X-ray diffraction measurements
are used to determine x and ek allowing Dxalloy to be decoupled and is estimated to be 12(64)
cm1/x for (100) GaAs1xBix. DxLO is measured to be roughly double for samples grown on
(311)B-oriented substrates to that of (100) GaAs. This large difference in redshift is accounted for
by examining the Bi induced strain, effects from alloying, and defects formed during high-index
(311)B crystal growth.

The effects of long time thermal annealing at 200 C on the optical
and structural properties of GaAs1xBix alloys were investigated by
X-ray diffraction (XRD), field emission scanning electron microscopy
(FESEM), high resolution transmission electron microscopy
(HRTEM) and photoluminescence (PL). FESEM images show that
bismuth islands nucleate on the surface and their diameter
increases after annealing. It was observed a PL intensity enhancement
and a small blue shift in PL peak energy after thermal annealing
at 200 C for 3 h of GaAs1xBix alloys which was associated to
the reduction of the density of defects. However these defects are
not completed removed by thermal annealing although an important
PL intensity improvement is observed.

Since its initial synthesis and investigation more than 40 years ago, the HgCdTe alloy semiconductor system has evolved into one of the primary infrared detector materials for high-performance infrared focal-plane arrays (FPA) designed to operate in the 3-5 µm and 8-12 µm spectral ranges of importance for thermal imaging systems. Over the course of the past decade, significant advances have been made in the development of thin-film epitaxial growth techniques, such as molecular-beam epitaxy (MBE), which have enabled the synthesis of IR detector device structures with complex doping and composition profiles. The central role played by in situ sensors for monitoring and control of the MBE growth process are reviewed. The development of MBE HgCdTe growth technology is discussed in three particular device applications: avalanche photodiodes for 1.55 µm photodetection, megapixel FPAs on Si substrates, and multispectral IR detectors.

Undoped GaSb is p-type with the residual acceptor concentration of about 1e17 cm-3 due to the gallium vacancies and gallium in antimony site. Counter-doping of GaSb with low level of Te can reduce the net carrier concentration resulting in higher optical transparency in a broad IR spectral range. In this work, the carrier concentration, mobility and sheet resistance of n-type and p-type Te-doped GaSb substrates were measured using Hall method at 300K and 77K. The Hall carrier concentration data at 300K were correlated with the absorption coefficients of GaSb in the IR spectral range. An empirical relationship between these values was established. Based on this correlation, we discuss application of FTIR spectroscopy for non-destructive optical screening of the substrates that allows construction of the carrier concentration distribution map across GaSb wafers. Investigations of the electronic properties of the low-doped p-type and n-type GaSb substrates upon cooling down to 77K indicate the reduction of the hole carrier concentration background for both GaSb types. This is evident from the decrease in the Hall-measured carrier concentration for p-type GaSb. For n-type GaSb, an increase in the carrier concentration is observed due to the reduction of the hole carrier concentration background.

We obtained light emission with a wavelength of 1242 nm at room temperature from self-assembled InAs quantum dots grown by molecular beam epitaxy (MBE) with interruption and embedded in the GaAs layer. Further, when a 6 nm InGaAs strain reducing layer was added the emission wavelength was around 1330 nm. The full width at half maximum is as narrow as 28.3 meV. InAs quantum dots with less size fluctuations were obtained on GaAs(100) substrate by using the growth interruption of 15 s for every 0.11 monolayer (ML) after depositing 1.9 ML of InAs continuously. Atomic force microscopy images show that the initial continuous growth up to 1.9 ML acted as a ''seed'' and helped to double the dot density. The subsequent supply of In with interruptions resulted in a large dot size while maintaining a high dot density. The six layer stacked (d ¼ 22 nm) quantum dots (QDs) grown with interruptions showed nearly 7 times stronger photoluminescence at room temperature than the continuously grown structure.