Neste trabalho estudamos experimentalmente, através da técnica de retroespalhamento de Rutherford, a distribuição de vários elementos C295. 2.15 83) implantados em filmes de Be, C e SiOz, na faixa de energia entre 10 e 400keV. Os resultados experimentais foram comparados com as predições teóricas desenvolvidas por Ziegler. Biersack e Littmark C2BL). Nossos resultados apresentam várias características distintas: para substratos de SiOz, obtivemos um acordo muito bom entre valores teóricos e experimentais do alcance projetado Rp e alguns desvios na largura do perfil de implantação ARp. Contudo, para os alvos de C e Be. encontramos grandes discrepâncias com os cálculos de ZBL. Para Bi, Pb, Au, Yb, Er, Eu e Cu em C e para Bi, Pb e Cu em Be. os valores experimentais de alcance excedem os teóricos em mais de 40%, ficando em média entre 25 e 30%. As diferenças são praticamente independentes da energia de implantação. Além disso, as larguras longitudinais do perfil de implantação também são fortemente subestimadas pelos cálculos Cchegando até a um fator 2). É mostrado que esses desacordos não podem ser atribuídos a imprecisões no potencial elástico ZBL ou ao poder de freamento eletrônico ZBL. Entretanto, se considerarmos a inclusão de colisões inelásticas no cálculo do poder de freamento nuclear, o poder de freamento total pode ser significativamente reduzido, nos casos de íons pesados incidindo em alvos leves. Como conseqüência deste tratamento, conseguimos obter um excelente acordo com os nossos resultados experimentais. / We have experimentally studied by using the Rutherford backscattering technique the range profiles of a variety of elements C29 5. 214 <83) implanted into Be, C and SiOz films at energies ranging from 10 to 400keV. The experimental results were compared with the predictions developed by Ziegler, Biersack and Littmark CZBL). Our results show several distinct features : for SiOz substrates , we have obtained an overall good agreement between the theoretical and experimental values of the projected ranges CRO and some deviations in the projected range stragglings CàRp). Instead for C and Be targets, we have found large discrepancies with the ZBL calculations. In fact, for Pb, Bi, Au, Yb, Er, Eu and Cu into C film and for Bi, Pb and Cu into Be film, the experimental range values exceed the theoretical oves by as much as 40% and on average around 25-30% . The differences are independent of the implantation energy. In addition, the range stragglings are also strongly under-estimated by the calculations Creaching up to a factor 2). It is shown that this disagreements can not be attributed to inaccuracies of the ZDL elastic potential or to the 2BL electronic stopping power. However if we consider the inclusion of inelastic collisions in the calculation of the nuclear stopping power, the total stopping power and the scattering angles CC.M. system) can be significantly reduced, mainly in the case of heavy ions impinging into light targets. As a consequence of this treatment, we have obtained an excellent agreement with our experimental data.

Estudamos o processo de dopagem de silício com antimônio por recuo promovido por bombardeamento iônico. Em nossas experiências o sistema filme fino de antimônio de 60 nm de espessura depositado sobre silício monocristalino de orientação <100> foi bombardeado com Ar+ ou Ge+ com energias entre 40 e 800 KeV e doses entre 1,0X1014 e 1,0X1017 cm². As amostras foram submetidas e recozimento térmico rápido a temperaturas entre 950 e 1150 ºC por tempos entre 20 e 60 s ou a recozimento prolongado em forno a 600 ºC por 1h. Algumas amostras foram submetidas a recozimento em duas etapas: prolongado a 600ºC por 1h seguido de recozimento rápido a 1200ºC por 5s. A análise das amostras foi feita empregando-se retroespalhamento Rutherford (RBS), espectrometria Auger e medidas em dispositivos Van der Pauw. Os principais resultados são: i) O processo que governa a implantação por recuo e a mistura balística induzida por colisões secundárias. ii) A concentração máxima de dopante situa-se na superfície e toda região dopada localiza-se a profundidade inferior a 0,1 um. iii) A largura do perfil de implantação independo da energia do projétil, e é função da dose incidente. Doses crescentes geram perfis mais profundos. iv) O bombardeamento com Ar+ resulta em recristalização inadequado do silício. O bombardeamento com Ge+ viabiliza perfeita recristalização do silício e boa substitucionalidade do dopante. / We investigated the doping process of silicon with antimony by means of the recoil implantation method. I our experiments a film of antimony deposited over <100> single cristal silicon was bombarded with Ar+ or Ge+ with energies between 40 and 800 KeV and doses ranging from 1,30C1014 to 1,0X1017 cm². Single step annealing of the bombarded samples was performed either in a Rapid Thermal Annealing (RTA) system or in a conventional furnace. IN the former case temperatures ranged from 950 to 1150 ºC and annealing times from 20 to 60s. In the latter case samples were annealed at 600ºC for 1 hour. The samples were analyzed by means of the Rutherford Backscattering spectrometry (RBS) technique Auger spectrometry and electrical measurements in Van der Pauw devices. The main results are: i) Recoil implantation ir governed by ballistic mixing process of collision cascades generated by the incident ions. ii) The maximum antimony concentration occours at the surface and decays rapidly with depth. The profile extends up to a maximum depth of 0,1um, even after annealing. iii) Antimony depth profile are independent of the bombarding particle’s energy, but are dependent on the dose. iv) Ar + bombardment yields imperfect recrystallization at the silicon substrate. Ge+ bombardment yields perfect recrystallization and good substitutionality of antimony atoms after annealing.

Neste trabalho, medimos a perda de energia de íons de He e B ao longo da direção < 100 > do Si, com energias que vão desde 200 ke V a 4,5 Me V, no primeiro caso, e de 500 ke V a 9 MeV, no segundo. Usamos a técnica de retroespalhamento de Rutherford com amostras do tipo SIMOX, as quais consistem de uma camada de Si monocristalino sobre uma camada de 500 nm de Si02 enterrada numa matriz de Si < 100 >. No método experimental empregado, a perda de energia dos íons canalizados é obtida depois de os mesmos serem retroespalhados em um marcador especialmente utilizado para esse fim. Para ambos os tipos de projétil, a curva da razão a entre os poderes de freamento de canalização e em direções aleatórias exibe um máximo largo e decresce lentamente a energias mais altas, em conseqüência do aumento da contribuição da camada L do Si para o poder de freamento eletrônico, como é indicado por cálculos de Aproximação de Born de Onda Plana (PWBA). / In this work, we have measured the electronic stopping power of He and B ions channeling along the < 100 > direction of Si crystals. The ion energies ranged between 200 keV and 4.5 Me V, in the first case, and between 500 ke V and 9 Me V, in the second one. We have used the Rutherford backscattering technique with SIMOX samples consisting of a Si single-crystal layer on top of a buried layer of 500 nm Si02 built into Si < 100 > wafer. In this exp erimental method, the channeling energy loss is obtained aft er the particles being backscattered at some marker specially used for this purpose . For both types of projectile, the curve of the a ratio between the channeling and random stopping powers has a broad maximum and decreases slowly at high energies dueto the increasing of the contribution of the Si L shell to the electronic stopping power, as indicated by Plane Wave Born Approximation (PWBA) calculations.

Neste trabalho estudamos experimentalmente, através da técnica de retroespalhamento de Rutherford, a distribuição de vários elementos C295. 2.15 83) implantados em filmes de Be, C e SiOz, na faixa de energia entre 10 e 400keV. Os resultados experimentais foram comparados com as predições teóricas desenvolvidas por Ziegler. Biersack e Littmark C2BL). Nossos resultados apresentam várias características distintas: para substratos de SiOz, obtivemos um acordo muito bom entre valores teóricos e experimentais do alcance projetado Rp e alguns desvios na largura do perfil de implantação ARp. Contudo, para os alvos de C e Be. encontramos grandes discrepâncias com os cálculos de ZBL. Para Bi, Pb, Au, Yb, Er, Eu e Cu em C e para Bi, Pb e Cu em Be. os valores experimentais de alcance excedem os teóricos em mais de 40%, ficando em média entre 25 e 30%. As diferenças são praticamente independentes da energia de implantação. Além disso, as larguras longitudinais do perfil de implantação também são fortemente subestimadas pelos cálculos Cchegando até a um fator 2). É mostrado que esses desacordos não podem ser atribuídos a imprecisões no potencial elástico ZBL ou ao poder de freamento eletrônico ZBL. Entretanto, se considerarmos a inclusão de colisões inelásticas no cálculo do poder de freamento nuclear, o poder de freamento total pode ser significativamente reduzido, nos casos de íons pesados incidindo em alvos leves. Como conseqüência deste tratamento, conseguimos obter um excelente acordo com os nossos resultados experimentais. / We have experimentally studied by using the Rutherford backscattering technique the range profiles of a variety of elements C29 5. 214 <83) implanted into Be, C and SiOz films at energies ranging from 10 to 400keV. The experimental results were compared with the predictions developed by Ziegler, Biersack and Littmark CZBL). Our results show several distinct features : for SiOz substrates , we have obtained an overall good agreement between the theoretical and experimental values of the projected ranges CRO and some deviations in the projected range stragglings CàRp). Instead for C and Be targets, we have found large discrepancies with the ZBL calculations. In fact, for Pb, Bi, Au, Yb, Er, Eu and Cu into C film and for Bi, Pb and Cu into Be film, the experimental range values exceed the theoretical oves by as much as 40% and on average around 25-30% . The differences are independent of the implantation energy. In addition, the range stragglings are also strongly under-estimated by the calculations Creaching up to a factor 2). It is shown that this disagreements can not be attributed to inaccuracies of the ZDL elastic potential or to the 2BL electronic stopping power. However if we consider the inclusion of inelastic collisions in the calculation of the nuclear stopping power, the total stopping power and the scattering angles CC.M. system) can be significantly reduced, mainly in the case of heavy ions impinging into light targets. As a consequence of this treatment, we have obtained an excellent agreement with our experimental data.

Neste trabalho, medimos a perda de energia de íons de He e B ao longo da direção < 100 > do Si, com energias que vão desde 200 ke V a 4,5 Me V, no primeiro caso, e de 500 ke V a 9 MeV, no segundo. Usamos a técnica de retroespalhamento de Rutherford com amostras do tipo SIMOX, as quais consistem de uma camada de Si monocristalino sobre uma camada de 500 nm de Si02 enterrada numa matriz de Si < 100 >. No método experimental empregado, a perda de energia dos íons canalizados é obtida depois de os mesmos serem retroespalhados em um marcador especialmente utilizado para esse fim. Para ambos os tipos de projétil, a curva da razão a entre os poderes de freamento de canalização e em direções aleatórias exibe um máximo largo e decresce lentamente a energias mais altas, em conseqüência do aumento da contribuição da camada L do Si para o poder de freamento eletrônico, como é indicado por cálculos de Aproximação de Born de Onda Plana (PWBA). / In this work, we have measured the electronic stopping power of He and B ions channeling along the < 100 > direction of Si crystals. The ion energies ranged between 200 keV and 4.5 Me V, in the first case, and between 500 ke V and 9 Me V, in the second one. We have used the Rutherford backscattering technique with SIMOX samples consisting of a Si single-crystal layer on top of a buried layer of 500 nm Si02 built into Si < 100 > wafer. In this exp erimental method, the channeling energy loss is obtained aft er the particles being backscattered at some marker specially used for this purpose . For both types of projectile, the curve of the a ratio between the channeling and random stopping powers has a broad maximum and decreases slowly at high energies dueto the increasing of the contribution of the Si L shell to the electronic stopping power, as indicated by Plane Wave Born Approximation (PWBA) calculations.

Estudamos o processo de dopagem de silício com antimônio por recuo promovido por bombardeamento iônico. Em nossas experiências o sistema filme fino de antimônio de 60 nm de espessura depositado sobre silício monocristalino de orientação <100> foi bombardeado com Ar+ ou Ge+ com energias entre 40 e 800 KeV e doses entre 1,0X1014 e 1,0X1017 cm². As amostras foram submetidas e recozimento térmico rápido a temperaturas entre 950 e 1150 ºC por tempos entre 20 e 60 s ou a recozimento prolongado em forno a 600 ºC por 1h. Algumas amostras foram submetidas a recozimento em duas etapas: prolongado a 600ºC por 1h seguido de recozimento rápido a 1200ºC por 5s. A análise das amostras foi feita empregando-se retroespalhamento Rutherford (RBS), espectrometria Auger e medidas em dispositivos Van der Pauw. Os principais resultados são: i) O processo que governa a implantação por recuo e a mistura balística induzida por colisões secundárias. ii) A concentração máxima de dopante situa-se na superfície e toda região dopada localiza-se a profundidade inferior a 0,1 um. iii) A largura do perfil de implantação independo da energia do projétil, e é função da dose incidente. Doses crescentes geram perfis mais profundos. iv) O bombardeamento com Ar+ resulta em recristalização inadequado do silício. O bombardeamento com Ge+ viabiliza perfeita recristalização do silício e boa substitucionalidade do dopante. / We investigated the doping process of silicon with antimony by means of the recoil implantation method. I our experiments a film of antimony deposited over <100> single cristal silicon was bombarded with Ar+ or Ge+ with energies between 40 and 800 KeV and doses ranging from 1,30C1014 to 1,0X1017 cm². Single step annealing of the bombarded samples was performed either in a Rapid Thermal Annealing (RTA) system or in a conventional furnace. IN the former case temperatures ranged from 950 to 1150 ºC and annealing times from 20 to 60s. In the latter case samples were annealed at 600ºC for 1 hour. The samples were analyzed by means of the Rutherford Backscattering spectrometry (RBS) technique Auger spectrometry and electrical measurements in Van der Pauw devices. The main results are: i) Recoil implantation ir governed by ballistic mixing process of collision cascades generated by the incident ions. ii) The maximum antimony concentration occours at the surface and decays rapidly with depth. The profile extends up to a maximum depth of 0,1um, even after annealing. iii) Antimony depth profile are independent of the bombarding particle’s energy, but are dependent on the dose. iv) Ar + bombardment yields imperfect recrystallization at the silicon substrate. Ge+ bombardment yields perfect recrystallization and good substitutionality of antimony atoms after annealing.

Neste trabalho estudamos experimentalmente, através da técnica de retroespalhamento de Rutherford, a distribuição de vários elementos C295. 2.15 83) implantados em filmes de Be, C e SiOz, na faixa de energia entre 10 e 400keV. Os resultados experimentais foram comparados com as predições teóricas desenvolvidas por Ziegler. Biersack e Littmark C2BL). Nossos resultados apresentam várias características distintas: para substratos de SiOz, obtivemos um acordo muito bom entre valores teóricos e experimentais do alcance projetado Rp e alguns desvios na largura do perfil de implantação ARp. Contudo, para os alvos de C e Be. encontramos grandes discrepâncias com os cálculos de ZBL. Para Bi, Pb, Au, Yb, Er, Eu e Cu em C e para Bi, Pb e Cu em Be. os valores experimentais de alcance excedem os teóricos em mais de 40%, ficando em média entre 25 e 30%. As diferenças são praticamente independentes da energia de implantação. Além disso, as larguras longitudinais do perfil de implantação também são fortemente subestimadas pelos cálculos Cchegando até a um fator 2). É mostrado que esses desacordos não podem ser atribuídos a imprecisões no potencial elástico ZBL ou ao poder de freamento eletrônico ZBL. Entretanto, se considerarmos a inclusão de colisões inelásticas no cálculo do poder de freamento nuclear, o poder de freamento total pode ser significativamente reduzido, nos casos de íons pesados incidindo em alvos leves. Como conseqüência deste tratamento, conseguimos obter um excelente acordo com os nossos resultados experimentais. / We have experimentally studied by using the Rutherford backscattering technique the range profiles of a variety of elements C29 5. 214 <83) implanted into Be, C and SiOz films at energies ranging from 10 to 400keV. The experimental results were compared with the predictions developed by Ziegler, Biersack and Littmark CZBL). Our results show several distinct features : for SiOz substrates , we have obtained an overall good agreement between the theoretical and experimental values of the projected ranges CRO and some deviations in the projected range stragglings CàRp). Instead for C and Be targets, we have found large discrepancies with the ZBL calculations. In fact, for Pb, Bi, Au, Yb, Er, Eu and Cu into C film and for Bi, Pb and Cu into Be film, the experimental range values exceed the theoretical oves by as much as 40% and on average around 25-30% . The differences are independent of the implantation energy. In addition, the range stragglings are also strongly under-estimated by the calculations Creaching up to a factor 2). It is shown that this disagreements can not be attributed to inaccuracies of the ZDL elastic potential or to the 2BL electronic stopping power. However if we consider the inclusion of inelastic collisions in the calculation of the nuclear stopping power, the total stopping power and the scattering angles CC.M. system) can be significantly reduced, mainly in the case of heavy ions impinging into light targets. As a consequence of this treatment, we have obtained an excellent agreement with our experimental data.

[No abstract available] / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A high sensitivity, wide or narrow band, double field modulation paramagnetic resonance spectrometer operating at a wavelength of 1.25 cm. for use at liquid helium temperatures has been developed which is described in detail. This spectrometer employs a transmission type cylindrical resonant cavity operated in the H₁₁₁ mode. In wide band operation, the magnetic field is modulated at 60 cps. to an-amplitude in excess of the resonance line width and at 462.5 kcs. to an amplitude less than or equal to the line width. For narrow band operation only, the high frequency modulation is employed and the static magnetic field is linearly swept. A signal from 10⁻⁹ grams of diphenyltrinitro phenyl hydrazyl [(C₆H₅)₂•N-N•C₆H₂•(NO₂)₃] has been observed at 290°K. using wide band operation (8 kcs.) indicating that sensitivities of the order of 10⁻¹² grams can be achieved with it at 4.2°K. in narrow band operation (1 cps.). This sensitivity is close to the theoretical value predicted by Bleaney of 10⁻¹³ grams and is several orders of magnitude greater than that reported for any other paramagnetic resonance spectrometer. Using this improved sensitivity, higher order transitions ΔM = ± 2, ± 3 in dilute gadolinium ethyl sulphate [4f⁷; ⁸s₇͵₂] which were not previously observable, have been studied at 90°K. as a function of the orientation of the magnetic field with respect to the axis of symmetry of the crystal. These transitions show that the effect of off-diagonal terms in spin-Hamiltonian have a greater effect on the energy levels than had previously been appreciated from measurements of the ΔM = ±1 transitions and help to explain the discrepancies between the calculated and observed zero field splittings. An excited state in dilute dysprosium ethyl sulphate [4f⁹; ⁸H₁₅͵₂] has been observed at 4.2°K. with g₁₁ =5.85 ± 0.05 which had previously only been observed at 20°K. with g₁₁ = 5.80 ± 0.02 and g⊥ = 8.40 ± 0.2. The line width of dilute praseodymium ethyl sulphate [4f²; 3H₄] has been measured at 4.2°K. and found to be 35 ± 5 gauss showing that the previously observed line width of 200 gauss at 20°K. is due to spin-lattice broadening. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The lifetime of the negative hydrogen ion in an electric field is of crucial importance for the design and performance of negative ion sector-focussed cyclotrons. The v x B force of the ion moving with a velocity v in a magnetic field B acts like an electric field which removes an electron from the ion. In previous calculations of the dissociation rate, a simple one-electron picture, in which the escaping electron moves in the field of a neutral H atom and tunnels through the barrier formed by the combination of the electric potential and the potential well of the neutral atom was used. We improve the best potential previously chosen by requiring the one-electron state of the second electron to be properly bound with the ionization energy of the H ̄ ion in the absence of the external field. The methods of nuclear reaction theory are then applied in an accurate calculation of the width. The disagreement between the calculated mean lifetime and the experimental values indicates this simple picture of the H ̄ ion is inadequate and the correlations between the two electrons are important. Therefore these are included by using an accurate two electron variational wavefunction. The form of the single particle state from which one of the electrons is removed is then defined unambiguously and a spectroscopic factor results which includes the two electron aspects of the problem. The calculated mean lifetime is then found to agree with the experimental values to within the accuracy of the two sets of results. / Science, Faculty of / Physics and Astronomy, Department of / Graduate